Data ONTAP 7.3 Data Protection Online Backup and Recovery Guide

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Data Protection

Online Backup and Recovery Guide

NetApp, Inc. 495 East Java Drive

Sunnyvale, CA 94089 U.S.A. Telephone: +1 (408) 822-6000 Fax: +1 (408) 822-4501

Support telephone: +1 (888) 4-NETAPP

Documentation comments: doccomments@netapp.com Information Web: http://www.netapp.com

Part number: 210-04755_A0

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Trademark information

All applicable trademark attribution is listed here.

NetApp, the Network Appliance logo, the bolt design, NetApp-the Network Appliance Company, Cryptainer, Cryptoshred, DataFabric, DataFort, Data ONTAP, Decru, FAServer, FilerView,

FlexClone, FlexVol, Manage ONTAP, MultiStore, NearStore, NetCache, NOW NetApp on the Web, SANscreen, SecureShare, SnapDrive, SnapLock, SnapManager, SnapMirror, SnapMover,

SnapRestore, SnapValidator, SnapVault, Spinnaker Networks, SpinCluster, SpinFS, SpinHA, SpinMove, SpinServer, StoreVault, SyncMirror, Topio, VFM, and WAFL are registered trademarks of NetApp, Inc. in the U.S.A. and/or other countries. gFiler, Network Appliance, SnapCopy, Snapshot, and The evolution of storage are trademarks of NetApp, Inc. in the U.S.A. and/or other countries and registered trademarks in some other countries. The NetApp arch logo; the StoreVault logo; ApplianceWatch; BareMetal; Camera-to-Viewer; ComplianceClock; ComplianceJournal; ContentDirector; ContentFabric; Data Motion; EdgeFiler; FlexShare; FPolicy; Go Further, Faster; HyperSAN; InfoFabric; Lifetime Key Management, LockVault; NOW; ONTAPI; OpenKey, RAID-DP; ReplicatorX; RoboCache; RoboFiler; SecureAdmin; SecureView; Serving Data by Design; Shadow Tape; SharedStorage; Simplicore; Simulate ONTAP; Smart SAN; SnapCache;

SnapDirector; SnapFilter; SnapMigrator; SnapSuite; SohoFiler; SpinMirror; SpinRestore; SpinShot; SpinStor; vFiler; VFM Virtual File Manager; VPolicy; and Web Filer are trademarks of NetApp, Inc. in the U.S.A. and other countries. NetApp Availability Assurance and NetApp ProTech Expert are service marks of NetApp, Inc. in the U.S.A.

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About this guide

You can use your product more effectively when you understand this document's intended audience and the conventions that this document uses to present information.

This guide describes how to protect, back up, restore, and copy data for systems that run Data ONTAP.

Next topics

Audience on page 21

Accessing Data ONTAP man pages on page 21

Terminology on page 22

Where to enter commands on page 23

Keyboard and formatting conventions on page 24

Special messages on page 25

How to send your comments on page 25

Audience

This document is written with certain assumptions about your technical knowledge and experience. This guide is for system administrators who are familiar with operating systems that run on the storage system’s clients, such as UNIX, Windows 95, Windows NT, and Windows 2000. You should be familiar with how to configure the storage system and how the NFS, CIFS, and HTTP protocols are used for file sharing or transfers. This guide does not cover basic system or network

administration topics, such as IP addressing, routing, and network topology; it emphasizes the characteristics of the storage system.

Accessing Data ONTAP man pages

You can use the Data ONTAP manual (man) pages to access technical information.

About this task

Data ONTAP manual pages are available for the following types of information. They are grouped into sections according to standard UNIX naming conventions.

Types of information Man page section

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Types of information Man page section

Special files 4

File formats and conventions 5

System management and services 8

Step

1. View man pages in the following ways:

• Enter the following command at the storage system command line:

man command_or_file_name

• Click the manual pages button on the main Data ONTAP navigational page in the FilerView user interface.

• Use the Commands: Manual Page Reference, Volumes 1 and 2 (which can be downloaded or ordered through the NOW site).

Note: All Data ONTAP man pages are stored on the storage system in files whose names are prefixed with the string "na_" to distinguish them from client man pages. The prefixed names are used to distinguish storage system man pages from other man pages and sometimes appear in the NAME field of the man page, but the prefixes are not part of the command, file, or services.

Terminology

To understand the concepts in this document, you might need to know how certain terms are used.

Storage terms

array LUN Refers to storage that third-party storage arrays provide to storage systems running Data ONTAP software. One array LUN is the equivalent of one disk on a native disk shelf.

LUN (logical unit number)

Refers to a logical unit of storage identified by a number.

native disk Refers to a disk that is sold as local storage for storage systems that run Data ONTAP software.

native disk shelf Refers to a disk shelf that is sold as local storage for storage systems that run Data ONTAP software.

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storage controller

Refers to the component of a storage system that runs the Data ONTAP operating system and controls its disk subsystem. Storage controllers are also sometimes called controllers, storage appliances, appliances, storage engines, heads, CPU modules, or controller modules.

storage system Refers to the hardware device running Data ONTAP that receives data from and sends data to native disk shelves, third-party storage, or both. Storage systems that run Data ONTAP are sometimes referred to as filers, appliances, storage appliances, V-Series systems, or systems.

third-party storage

Refers to the back-end storage arrays, such as IBM, Hitachi Data Systems, and HP, that provide storage for storage systems running Data ONTAP.

Cluster and high-availability terms active/active

configuration

In the Data ONTAP 7.2 and 7.3 release families, refers to a pair of storage systems (sometimes called nodes) configured to serve data for each other if one of the two systems stops functioning. Also sometimes referred to as active/active pairs. In the Data ONTAP 7.1 release family and earlier releases, this

functionality is referred to as a cluster.

cluster In the Data ONTAP 7.1 release family and earlier releases, refers to a pair of storage systems (sometimes called nodes) configured to serve data for each other if one of the two systems stops functioning. In the Data ONTAP 7.3 and 7.2 release families, this functionality is referred to as an active/active configuration.

Where to enter commands

You can use your product more effectively when you understand how this document uses command conventions to present information.

You can perform common administrator tasks in one or more of the following ways:

• You can enter commands either at the system console or from any client computer that can obtain access to the storage system using a Telnet or Secure Shell (SSH) session.

In examples that illustrate command execution, the command syntax and output shown might differ from what you enter or see displayed, depending on your version of the operating system. • You can use the FilerView graphical user interface.

For information about accessing your system with FilerView, see the Data ONTAP System Administration Guide.

• You can enter Windows, ESX, HP-UX, AIX, Linux, and Solaris commands at the applicable client console.

In examples that illustrate command execution, the command syntax and output shown might differ from what you enter or see displayed, depending on your version of the operating system. • You can use the client graphical user interface.

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Your product documentation provides details about how to use the graphical user interface. • You can enter commands either at the switch console or from any client that can obtain access to

the switch using a Telnet session.

In examples that illustrate command execution, the command syntax and output shown might differ from what you enter or see displayed, depending on your version of the operating system.

Keyboard and formatting conventions

You can use your product more effectively when you understand how this document uses keyboard and formatting conventions to present information.

Keyboard conventions Convention What it means

The NOW site Refers to NetApp On the Web at http://now.netapp.com/.

Enter, enter • Used to refer to the key that generates a carriage return; the key is named Return on some keyboards.

• Used to mean pressing one or more keys on the keyboard and then pressing the Enter key, or clicking in a field in a graphical interface and then typing information into the field.

hyphen (-) Used to separate individual keys. For example, Ctrl-D means holding down the Ctrl key while pressing the D key.

type Used to mean pressing one or more keys on the keyboard.

Formatting conventions

Convention What it means

Italic font • Words or characters that require special attention. • Placeholders for information that you must supply.

For example, if the guide says to enter the arp -dhostname command, you enter the characters "arp -d" followed by the actual name of the host. • Book titles in cross-references.

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Convention What it means

Monospaced font • Command names, option names, keywords, and daemon names.

• Information displayed on the system console or other computer monitors. • Contents of files.

• File, path, and directory names.

Bold monospaced

font

Words or characters you type. What you type is always shown in lowercase letters, unless your program is case-sensitive and uppercase letters are necessary for it to work properly.

Special messages

This document might contain the following types of messages to alert you to conditions that you need to be aware of.

Note: A note contains important information that helps you install or operate the system efficiently.

Attention: An attention notice contains instructions that you must follow to avoid a system crash, loss of data, or damage to the equipment.

How to send your comments

You can help us to improve the quality of our documentation by sending us your feedback.

Your feedback is important in helping us to provide the most accurate and high-quality information. If you have suggestions for improving this document, send us your comments by e-mail to

doccomments@netapp.com. To help us direct your comments to the correct division, include in the subject line the name of your product and the applicable operating system. For example, FAS6070— Data ONTAP 7.3, or Host Utilities—Solaris, or Operations Manager 3.8—Windows.

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Introduction to data protection

Data protection means backing up data and being able to recover it. You protect the data by making copies of it so that it is available for restoration even if the original is no longer available.

Businesses need data backup and protection for the following reasons.

• To protect data from accidentally-deleted files, application crashes, data corruption, and viruses • To archive data for future use

• To recover from a disaster

Next topics

Methods of protecting data on page 27

What online backup and recovery is on page 29

What the NVFAIL feature is on page 32

What a data loss disaster is on page 32

How to protect data in a SAN environment on page 35

Policy-based automated data protection using Protection Manager on page 35

Methods of protecting data

Depending on your data protection and backup needs, Data ONTAP offers a variety of features and methods to ensure against accidental, malicious, or disaster-induced loss of data.

Data protection feature Description

aggr copy This is fast block copy of data stored in aggregates; it enables you to quickly copy blocks of stored system data from one aggregate to another.

Snapshot copy Backup within a volume.

This feature allows you to manually or automatically create, schedule, and maintain multiple backups (also called Snapshot copies) of data on a volume. Snapshot copies use only a minimal amount of additional volume space, and do not have a performance cost.

If a user accidentally modifies or deletes crucial data on a volume with Snapshot enabled, that data can be easily and quickly restored from one of the last several Snapshot copies taken.

You can also create clones of FlexVol volumes and Data ONTAP LUNs using Snapshot copies. For more details, see the Data ONTAP Storage Management Guide.

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SnapRestore (license required) Fast, space-efficient restoration of large volumes of data backed up to Snapshot copies.

The SnapRestore feature performs on-request Snapshot recovery from Snapshot copies on an entire volume.

SnapMirror (license required) Volume-to-volume and qtree-to-qtree replication.

This feature enables you to periodically make Snapshot copies of data on one volume or qtree, replicate that data to a partner volume or qtree, usually on another storage system, and archive one or more iterations of that data as Snapshot copies. Replication on the partner volume or qtree ensures quick availability and restoration of data, from the point of the last Snapshot copy, should the storage system containing the original volume or qtree be disabled.

If you conduct tape backup and archival operations, you can carry them out on the data already backed to the SnapMirror partner, thus freeing the original storage system of this time-consuming, performance-degrading chore.

SnapVault (license required) Centralized backup of multiple qtrees on multiple storage systems using Snapshot technology.

This feature enables you to back up qtrees on multiple volumes and storage systems to a single SnapVault secondary storage system specialized for quick backup and restore of its sources.

You can also install the Open Systems SnapVault agent on Windows, Solaris, Linux, AIX, or HP-UX systems. This agent enables SnapVault to back up and restore data to these systems also.

If you conduct tape backup and archival operations, you can carry them out on the data already backed up to the SnapVault secondary storage system, thus freeing your storage system of this time-consuming, performance-degrading chore.

Tape backup dump and restore

commands

Tape backup and restore.

The dump and restore commands allow you to back up Snapshot copies to tape. The dump command takes a Snapshot copy of the volume and then copies that data to tape. Because the Snapshot copy, not the active file system, is backed up to tape, Data ONTAP can continue its normal functions while the tape backup takes place. For more information, see the Data ONTAP Data Protection Tape Backup and Recovery Guide.

vol copy _{Fast block-copy of data from one volume to another.}

The vol copy command enables you to quickly block copy stored data from one volume to another.

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SyncMirror (active/active configuration required)

Continuous mirroring of data to two separate aggregates. This feature allows for real-time mirroring of data to matching aggregates physically connected to the same storage system. In case of an unrecoverable disk error on one volume, the storage system automatically switches access to the mirrored volume. This feature requires an active/active configuration.

nvfail option to the vol options command

Protection against data corruption by failures of nonvolatile RAM (NVRAM).

SnapValidator (license required) Detects and rejects invalid Oracle data before it is written to the storage system.

Virus scan support _{Support for third-party virus-scanning software for files accessed by} CIFS clients.

MetroCluster Stretch MetroCluster provides site protection within a campus, and supports replication up to 500m. Fabric MetroCluster provides site protection within a metro, and supports replication up to 100 km using FC switches. SyncMirror functionality is enhanced to provide continuous volume mirroring.

For V-Series systems, Fabric MetroCluster support is limited to 30 km.

Related concepts

Data recovery using SnapRestore on page 71

Data protection using SnapVault on page 225

Data replication using volume copy on page 333

Data protection using SnapMirror on page 81

Virus protection for CIFS on page 395

Database protection using SnapValidator on page 385

Related references

Data mirroring using SyncMirror on page 349

What online backup and recovery is

Data ONTAP creates online data backups to enable online data recovery. Online backup data is stored on disks, or on array LUNs in the case of third-party storage, rather than on tape. Data stored on disk is available for quick restoring in the event that disaster recovery operations are necessary. Online backup and recovery solutions include: Snapshot, SnapMirror, SnapRestore, SnapVault, SyncMirror, MetroCluster, the vol copy command, and the ndmpcopy command.

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• The Snapshot feature enables you to schedule weekly, daily, or hourly online backups. Snapshot technology makes online point-in-time copies in the same volume as the original data. It enables users to recover their own deleted or modified files without assistance from a system

administrator.

• The SnapMirror feature allows you to schedule regular automatic copies of file system Snapshot copies of a volume or qtree onto another volume or qtree (on the same or a different storage system).

• The SnapRestore feature restores an entire volume to the state recorded in a previously created Snapshot copy with maximum speed and disk space efficiency. The SnapVault feature protects the data in one or more qtrees in a series of Snapshot copies stored on a separate storage system. • SnapVault maintains an online, asynchronous, permanently read-only replica of the qtree data.

SnapVault backup and Snapshot copy creation runs on an automated schedule.

Note: SnapVault, in addition to providing storage system backup, also provides direct backup to servers running Windows NT, Windows 2000, Solaris, or HP-UX.

• SyncMirror provides continuous real-time mirroring of data between two partner volumes on a shared or partner storage system.

• The MetroCluster feature provides SyncMirror continuous mirroring over extended distances (500 meters to 100 kilometers). For V-Series, Fabric MetroCluster support is limited to 30 km. • The vol copy command uses a Snapshot copy and copies a volume, manually or by means of a

script.

• The ndmpcopy command copies any subtree to any location on any storage system. For more information, see the Data ONTAP Data Protection Tape Backup and Recovery Guide.

You can use these online data backup and recovery systems to supplement tape backup and recovery.

Next topics

Advantages of online backup and recovery on page 30

Disadvantages of online backup and recovery on page 31

Methods for online backup and recovery on page 31

Advantages of online backup and recovery

Online backup and recovery protection offers better speed and ease of use, compared to tape archives.

The main advantages of online backup and recovery are as follows. • Speedy backups and restores greatly reduce backup time requirements. • Backups can be made more frequently because they are faster.

• It is easy to recover a particular file, directory, or volume from an online backup. • Disaster recovery is quicker with online mirroring and restores.

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• Data availability is higher because of the high speed of data recovery. • More data can be backed up in less time.

Disadvantages of online backup and recovery

Online data protection has some disadvantages over tape archives.

The important disadvantages of online backup and recovery compared to tape archives are the following.

• Online data protection is often more expensive to procure.

• Online data protection consumes resources, such as disk space, that can otherwise be used for everyday activities.

Methods for online backup and recovery

You can perform online backup and recovery using several methods.

Data ONTAP provides the following features for online backup and recovery: • Snapshot copies to make a read-only image of a file system on the same disk • SnapRestore to restore data to a corrupted volume from a previous Snapshot copy

• SnapMirror to maintain a replica of one volume in another volume, and one qtree in another qtree • SnapVault to keep copies of volumes on the server, from which individual qtrees are available at

any time to the client

• The vol copy command to copy data from one volume to another • SyncMirror to maintain two identical copies of a volume at all times

Snapshot management on page 37

Data recovery using SnapRestore on page 71

Data replication using volume copy on page 333

Related references

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What the NVFAIL feature is

If NVRAM problems occur that compromise database validity, the NVFAIL feature can warn you and automatically rename the database so that it does not restart automatically. You can then ensure that the database is valid before restarting it.

Data ONTAP provides database protection using the nvfail option of the vol options command.

Note: You can use this feature only when there are databases on the storage system.

Database protection using NVFAIL on page 381

What a data loss disaster is

A data loss disaster is a situation in which service from one physical site (for example, a building or a corporate campus) on the network is lost for an extended period of time.

The following are examples of disasters: • Fire

• Earthquake

• Prolonged power outages at a site

• Prolonged loss of connectivity from clients to the storage system at a site

When a disaster occurs, it can affect all the computing infrastructure including storage systems, application servers, networking connectivity, and client connectivity. When you create a disaster plan, you should take into consideration all of your computing infrastructure.

Next topics

How to determine a disaster on page 32

What tools to use to protect against data-loss disasters on page 33

How to determine a disaster

It is critical that you follow some predefined procedure to confirm whether a disaster really has occurred.

You can use any of the following procedures to determine the status of the supposed disaster site. • Use the following external interfaces:

• Ping

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• FilerView

• Protection Manager

• Use network management tools to test connectivity to the site. • Physically inspect the site, if possible.

What tools to use to protect against data-loss disasters

Data ONTAP provides features and products that enable the administrator to back up or replicate data stored on a local storage system to an off-site network location. This ensures that data can be restored if data loss is caused by disaster at a primary data storage site.

The following table describes the Data ONTAP tools that enable data protection.

Feature Description

SnapVault: Inter-site Snapshot

copy backup and restorability

A SnapVault secondary system can be located off-site, any distance from the primary storage systems that it is backing up.

Data recoverability: In the event of a data-loss disaster at a primary storage

site, data that is backed up to the SnapVault secondary storage can be restored to primary storage systems that have not suffered physical damage or that have been replaced either at the disaster site or at an alternate location.

Currency of restore: Data can be restored from the time that the last

Snapshot copy was created on the secondary system.

Connection requirements: DSL connections or faster are recommended

between the primary and secondary systems. Even connections with very low bandwidth, such as 56 Kbps, are possible.

Routers, switches, and DNS servers should be preconfigured to direct users to alternate storage sites if the primary system that they first attempt to access becomes unavailable.

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Feature Description SnapMirror: Inter-site

Snapshot copy backup, availability, and restorability

A SnapMirror destination system can be located off-site, any distance from the source system whose volumes it is replicating.

Data availability: In the event of a data-loss disaster at a source site,

SnapMirror data at the destination site can be made quickly available.

Data recoverability: SnapMirror data can be restored to source storage

systems that have not suffered physical damage or that have been replaced either at the disaster site or at an alternate location.

Currency of restore: Data can be restored from the time of the last

SnapMirror Snapshot copy transfer from source to destination.

Connection requirements: DSL connections or faster are recommended

between the source and destination. Even connections with very low bandwidth, such as 56 Kbps, are possible. Routers, switches, and DNS servers should be preconfigured to direct users to the destination storage site if the source they are attempting to access becomes unavailable.

Advantage: Combined off-site protection and availability MetroCluster: Inter-site

realtime backup, availability, and restorability

Synchronously mirrored MetroCluster storage systems can be located at different sites, up to 100 km from one another. For V-Series systems, Fabric MetroCluster support is limited to 30 km.

Data availability: In the event of a data-loss disaster at one site, data that

has been mirrored to the partner site can be made quickly available.

Data recoverability: This data can also be mirrored to source storage units

that have not suffered physical damage or that have been replaced either at the disaster site or at an alternate location.

Currency of restore: Data can be restored from the time of the last

NVRAM checkpoint.

Connection requirements: Data ONTAP cluster connections supplemented

with switches and DSL or faster connections are required. Routers, switches, and DNS servers should be preconfigured to direct users to the MetroCluster partner if the clustered system that they first attempt to access becomes unavailable.

Advantage: Combined real-time off-site protection and availability. For more information about MetroCluster, see the Data ONTAP Active/Active Configuration Guide.

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How to protect data in a SAN environment

If the volumes contain logical units of storage (LUNs) created to enable integration into a storage area network (SAN) environment, the procedures to implement data protection might have to be modified.

For descriptions of data backup and restore on volumes containing Data ONTAP LUNs, see the Data ONTAP Block Access Management Guide for iSCSI and FC.

Policy-based automated data protection using Protection

Manager

Typically, data and resource management is time consuming because it involves manual analysis and management of storage capacity, network bandwidth, schedules, retention policies, and other

infrastructure variables. Protection Manager simplifies this work by employing configuration policies (that you can assign to multiple storage systems, volumes, or qtrees), convenient wizards, and automated verification of certain aspects of the data protection configuration.

The protection application can perform the following actions:

• Use protection policies to manage primary data, storage, and backup and mirror relationships. • Manage local and remote backups and mirror copies.

• Provision the secondary storage for backups and mirrored copies based on policies you assign. • Enable disaster recovery capability if you install the licensed disaster recovery option. • Automatically validate your backup and disaster recovery configuration with a conformance

checker.

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Snapshot management

Data ONTAP maintains a configurable Snapshot schedule that creates and deletes Snapshot copies automatically for each volume. You can also create and delete Snapshot copies, and manage Snapshot schedules based on your requirements.

Next topics

What a Snapshot copy is on page 37

User access to Snapshot copies on page 39

How Data ONTAP Snapshot copies work in an iSCSI or FC network on page 42

Restoring files from Snapshot copies on page 44

Creation of Snapshot copy schedules on page 44

Creating Snapshot copies manually on page 50

Why you might need to access a particular Snapshot copy on page 50

What Snapshot disk consumption is on page 52

What file folding means and how it saves disk space on page 61

Displaying the rate of change between Snapshot copies on page 62

Deleting Snapshot copies automatically on page 64

Displaying space reclaimed from deleted Snapshot copies on page 67

How to determine which Snapshot copies to delete on the basis of size on page 67

Renaming Snapshot copies on page 70

What a Snapshot copy is

A Snapshot copy is a read-only image of a traditional volume, a FlexVol volume, or an aggregate that captures the state of the file system at a point in time. Snapshot copies are your first line of defense to back up and restore data.

For information about traditional volumes, FlexVol volumes, or aggregates, see the Data ONTAP Storage Management Guide.

Data ONTAP maintains a configurable Snapshot copy schedule that creates and deletes Snapshot copies automatically for each volume. Snapshot copies can also be created and deleted manually. You can store up to 255 Snapshot copies at one time on each volume.

You can specify the percentage of disk space that Snapshot copies can occupy. The default setting is 20 percent of the total (both used and unused) space on the disk.

Next topics

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What you can do with Snapshot copies on page 38

Creation of Snapshot copy schedules on page 44

What Snapshot disk consumption is on page 52

How Snapshot copies handle file permissions

Snapshot files carry the same permissions and inode numbers as the original files, keeping the integrity of the security system intact.

Inodes are data structures that hold information (including permissions information) about files on the storage system. Every file in the file system is uniquely identified by its inode in the same file system.

Note: The inode number for a file in a Snapshot copy is the same as the inode number for the corresponding file in the active file system. As a result, some programs on UNIX clients consider the two files to be the same. For example, if you use an older version of the GNU diff program to compare the two files, it might not find any differences between them. However, newer versions of GNU diff should work. In a few cases, if you try to restore a file from a Snapshot copy, you might see the following error message:

cp:.snapshot/xxx and xxx are identical.

To ensure that the two files have different inode numbers before the copying or comparison, copy one of the files to a different name.

What you can do with Snapshot copies

Snapshot copies enable system administrators and end users to perform important tasks in backup and recovery.

Snapshot copies enable system administrators to perform the following tasks: • Create instantaneous backups

• Create a clone of a FlexVol volume • Create a clone of a Data ONTAP LUN

For information about cloning a Data ONTAP LUN, see the Data ONTAP Block Access Management Guide for iSCSI and FC.

For information about cloning a FlexVol volume, see the Data ONTAP Storage Management Guide. Snapshot copies enable end users to do the following:

• Recover older versions or sets of files that were accidentally changed or deleted • Restore their own files without needing a system administrator to restore files from tape

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User access to Snapshot copies

By default, every volume contains a directory named .snapshot through which users can access old versions of files in that directory. Users can gain access to Snapshot copies depending on the file-sharing protocol used—NFS or CIFS. Access to Snapshot copies can be turned off.

Snapshot files carry the same read permissions as the original file. A user who has permission to read a file in the volume can read that file in a Snapshot copy. A user without read permission to the volume cannot read that file in a Snapshot copy. Snapshot copies do not have write permissions.

Next topics

Access to Snapshot copies over NFS on page 39

Access to Snapshot copies over CIFS on page 40

Accessing Snapshot copies from CIFS clients on page 41

Restricting access to Snapshot copies on page 41

Access to Snapshot copies over NFS

On an NFS client, the user can obtain access to Snapshot copies.

The following illustration shows the directory structure on an NFS client with the vol0 volume named toaster mounted on the /n/toaster directory.

Figure 1: Directory structure of an NFS client

In this example, the user can obtain access to Snapshot copies in the /n/toaster/.snapshot directory. Notice that the .snapshot directory is shown only at the mountpoint, although it actually

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exists in every directory in the tree. The user, however, can only see the .snapshot directory at the mountpoint. That is, the .snapshot directory is accessible by name in each directory, but is only seen in the output of the ls command at the mountpoint.

For example, at the mountpoint of a file system, a directory listing looks like this:

systemA> ls -a

. .. .snapshot dir1 dir2

The same command entered in a directory below the mountpoint does not show the .snapshot directory; for example:

systemA> cd dir1 systemA> ls -a . .. file1 file2

If you enter the ls command with the directory name .snapshot, you can see a directory for each of the Snapshot copies for the dir1 directory:

systemA> ls .snapshot

hourly.0 hourly.4 nightly.0 nightly.4 hourly.1 hourly.5 nightly.1 nightly.5 hourly.2 hourly.6 nightly.2 weekly.0 hourly.3 hourly.7 nightly.3 weekly.1

If the .snapshot directory entry appeared in every directory, it would cause many commands to work improperly. For instance, all recursive commands for deleting files would fail because everything below the .snapshot directory is read-only. The recursive commands would copy everything in the Snapshot copies as well as files in the active file system. A find command would generate a list much longer than expected.

Access to Snapshot copies over CIFS

By default, CIFS users cannot see the .snapshot directory. To allow CIFS users to see the .snapshot directory, you can set the cifs.show_snapshot option to on.

To CIFS users, the .snapshot directory appears only at the root of a share. For example, if a user’s home directory is a share named bill that corresponds to the /vol/vol0/home/bill directory, only the /vol/vol0/home/bill/.snapshot directory is visible. When this user displays the contents of the home directory, the .snapshot directory is displayed as ~snapshot if the operating system supports long file names and as ~SNAPSHT if the operating system supports only short file names.

Note: The .snapshot directory can be viewed in a directory listing or Windows Explorer display if the client operating system is configured to show hidden files.

In each directory within the share, a snapshot directory exists but is not visible to clients. For example, if the client operating system supports long file names, the applications on that operating system can use the Snapshot copy at each level of the share by using .snapshot, ~snapshot, or

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~SNAPSHT as the directory name. The user cannot, however, display the directory name in any listing.

Accessing Snapshot copies from CIFS clients

You can access the data within Snapshot copies from CIFS clients.

Before you begin

Ensure that the cifs.show_snapshot option is set to on.

Step

1. To access Snapshot copies on Windows NT 4 or other Windows clients (Windows 95 or later),

click Start > Run menu, then enter the following command:

\\systemname\share\.snapshot (or ~snapshot or ~SNAPSHT)

systemname is the name of the storage system you are using.

share is the name of the Windows share that you want to access. Example

\\systemA\home\.snapshot

Snapshot copies can also be accessed lower in the share by providing a path to a lower directory. Snapshot copies can be accessed through DOS on any system by changing to the ~SNAPSHT directory.

Restricting access to Snapshot copies

You can restrict client access to Snapshot copies for a particular volume. This restriction could be due to security issues, or to prevent access to virus-infected files. You can enable or disable client access by using the vol options command.

Step

1. To specify client access to Snapshot copies within a volume, enter the following command.

vol options vol_name nosnapdir {on|off}

vol_name is the name of the volume for which you want to set client access to Snapshot copies. You can set the nosnapdir option to either on or off.

• on - Disables client access to Snapshot copies, and hides the .snapshot directory from clients.

• off - Enables client access to Snapshot copies, and makes the .snapshot directory visible to clients.

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Disabling client access to Snapshot copies

To disable client access to Snapshot copies within the volA volume, enter the following command.

vol options volA nosnapdir on

How Data ONTAP Snapshot copies work in an iSCSI or FC

network

If you take a Snapshot copy of a file system when an application is running, the Snapshot copy might contain inconsistent data. You can take measures (such as quiescing the application) to ensure that the data is consistent before you take the Snapshot copy.

To take a Snapshot copy of these types of applications, you should ensure that the files are closed and cannot be modified. When you quiesce an application or take it offline, the file system caches are committed before the Snapshot copy is taken. The Snapshot copy takes less than one second to complete, after which the application can resume normal operation.

Some applications take a lot of time to quiesce. To avoid a scenario in which the application is unavailable for a long time, some applications have a built-in hot backup mode. This allows a Snapshot copy or a backup to occur while the application operates in a degraded mode, with limited performance.

Data ONTAP cannot take Snapshot copies of applications that have the ability to work with raw device partitions. It is recommended that you use specialized modules from a backup software vendor tailored for such applications.

To back up raw partitions, it is best to use hot backup mode for the duration of the backup operation. For more information about backup and recovery of databases using SAN configurations, see the appropriate technical report for the database.

Next topics

Using Snapshot copies in the SAN environment on page 42

Relationship between a LUN and a Snapshot copy on page 43

Related information

www.netapp.com/tech_library/

Using Snapshot copies in the SAN environment

You can use Snapshot copies in the SAN environment when the data within a Data ONTAP LUN is in a consistent state.

About this task

Data ONTAP cannot ensure that the data within a LUN is in a consistent state. That is, Data ONTAP does not know whether an application is accessing the data inside the LUN. Therefore, before

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creating a Snapshot copy, you need to quiesce the application or file system using the LUN. This action flushes the host file system buffers to disk. Quiescing ensures that the Snapshot copy is consistent.

One way to accomplish this is to use batch files and scripts on a host that has administrative access to the system.

Steps

1. Make the data within the LUN consistent with the application by quiescing a database, placing

the application in hot backup mode, or taking the application offline.

2. Use the rsh or ssh command in the script to access the system.

3. Use the snap command to create the Snapshot copy on the system (this takes only a few seconds, regardless of volume size or use).

4. Return the application to normal operation.

Snapshot copy scripts can be scheduled to run at specified intervals. On Windows hosts, you can use the Windows Task Scheduler. On UNIX hosts, you can use cron or other utilities. Also, you can use SnapDrive to save the contents of the host file system buffers to disk and to create Snapshot copies. For more information, see the SnapDrive Installation and Administration Guide.

Relationship between a LUN and a Snapshot copy

When you take a Snapshot copy of a Data ONTAP LUN, the Snapshot copy is initially backed by data in the LUN. After the Snapshot copy is taken, data written to the LUN is available in the active file system.

After you have a Snapshot copy, you can use it to create a LUN clone for temporary use as a

prototype for testing data or scripts in applications or databases. Because the LUN clone is backed by the Snapshot copy, you cannot delete the Snapshot copy until you split the clone from it.

To restore the LUN from a Snapshot copy, you can use SnapRestore. However, the restored LUN does not have any updates to the data since the Snapshot copy was taken.

When you create the LUN, space reservation is enabled by default. This means that enough space is reserved so that write operations to the LUNs are guaranteed. The more space that is reserved, the less free space is available. If free space within the volume is below a certain threshold, Snapshot copies cannot be taken.

Data ONTAP 7.3 Data Protection Online Backup and Recovery Guide

Data Protection

Online Backup and Recovery Guide

Contents

Copyright information ... 17

Trademark information ... 19

About this guide ... 21

Introduction to data protection ... 27

Snapshot management ... 37

Data recovery using SnapRestore ... 71

Data protection using SnapMirror ... 81

Data protection using SnapVault ... 225

Data replication using volume copy ... 333

Data mirroring using SyncMirror ... 349

Database protection using NVFAIL ... 381

Database protection using SnapValidator ... 385

Virus protection for CIFS ... 395

Glossary ... 415

Copyright information

Trademark information

About this guide

Audience

Accessing Data ONTAP man pages

Terminology

Where to enter commands

Keyboard and formatting conventions

Special messages

How to send your comments

Introduction to data protection

Methods of protecting data

What online backup and recovery is

Advantages of online backup and recovery

Disadvantages of online backup and recovery

Methods for online backup and recovery

What the NVFAIL feature is

What a data loss disaster is

How to determine a disaster

What tools to use to protect against data-loss disasters

How to protect data in a SAN environment

Policy-based automated data protection using Protection

Manager

Snapshot management

What a Snapshot copy is

How Snapshot copies handle file permissions

What you can do with Snapshot copies

User access to Snapshot copies

Access to Snapshot copies over NFS

Access to Snapshot copies over CIFS

Accessing Snapshot copies from CIFS clients

Restricting access to Snapshot copies

How Data ONTAP Snapshot copies work in an iSCSI or FC

network

Using Snapshot copies in the SAN environment

Relationship between a LUN and a Snapshot copy