EMC Centera data retention uses the bckendreten mount option to provide a mechanism to prevent the following data operations in the file system and on the back-end system:
◆ Overwrite
◆ Truncation
◆ Removal
◆ Modification of its metadata
◆ Modification of its retention period
These operations cannot be initiated in the file system or on the EMC Centera by any process, including non-FSM processes, for files that have been migrated or that are eligible for migration. A file is eligible for migration if it has not been modified for at least the period specified in the file system’s Delay Until Migrate Candidacy value.
When a file is subject to EMC Centera data retention, the file’s data cannot be changed during the retention period, in the file system or on the EMC Centera. Data on a secondary back-end system is not protected by this data retention mechanism.
Performance impact
UTDM file systems that are mounted with the bckendreten mount option generate a retention event to the core processes when a file modification operation is attempted. This event determines whether the modification is allowed.
The core processes instruct the UTDM file system to deny the attempt if either of the following is true for a file:
◆ The file is migrated and there is an unexpired retention period for its data on the EMC Centera.
◆ The file is not migrated and has not been modified within the period specified in the file system’s Delay Until Migrate Candidacy value. There is also a Centera Retention Period or Centera Retention Class associated with the file.
The retention events can have a performance impact on file
modification operations. A slight impact can occur because the core
processes must query the EMC Centera for the applicable retention period.
Retention events will not adversely impact normal file creation operations. UTDM file systems do not generate a retention event during the first minute after a file is created or modified.
Requirements EMC Centera data retention requires the following:
◆ The EMC Centera must use one of the following license models:
• Basic Compliance
• Compliance Plus
◆ The UTDM file system must use the EMC Centera as its primary back-end system.
◆ The UTDM file system configuration must specify at least one of the following:
• A value in Retention Class
• A value in Retention Period other than None
• An extended rule that sets a retention period or retention class
◆ The file system must be mounted with the bckendreten mount option.
◆ The FSM host system and the Centera should be in the same timezone for retention to be in sync.
Enabling EMC Centera data retention
To set EMC Centera data retention periods, first enable retention for the file system. Retention is specified by using the bckendreten option when mounting the file system.
To enable EMC Centera data retention for a file system:
1. Log in to the file system’s host as root.
2. Set the FSM environment.
“Setting the FSM environment” on page 177for more information.
3. Stop all FSM processes:
kill.fsm
4. If the file system is mounted, unmount it:
umount [-f] /file-system
where /file-system is the full path to the file system’s mount point.
Note:On Linux systems, the -f option must be used when you unmount a UTDM type file system. This is because the file system is viewed as busy by the operating system.
5. Mount the file system by using one of the methods shown in Table 33 on page 112.
The variables for the procedures shown inTable 33are as follows:
• fstype is the native type of the file system.
• blkdev is the full path to the block special device.
• mntpnt is the full path to the mount point.
• chardev is the full path to the character special device.
• log is the log file that is generated for the logical volume.
Table 33 Mounting with EMC Centera data retention (page 1 of 2) Mounting method Procedure
Command line (All operating systems, except Linux and AIX)
As root, run the following mount command:
mount-F utdm -o fstype=fstype,bckendreten /blkdev /mntpnt
Command line (Linux only)
As root, run the following mount command:
mount-t utdm -o fstype=fstype,bckendreten /blkdev /mntpnt
Command line (AIX only)
As root, run the following mount command:
mount-V utdm -o fstype=fstype,bckendreten /blkdev /mntpnt
6. Restart the FSM processes:
rc.fsm
EMC Centera data retention is enabled for the file system.
Setting retention for a file system
To set EMC Centera data retention for all files in a file system:
1. Mount the file system by using the bckendreten mount option.
“Enabling EMC Centera data retention” on page 111provides more information.
2. Start Console Client and log in to the management domain that controls the file system’s FSM host.
“How to start Console Client” on page 24describes how to start Console Client and log in to a management domain.
3. On the tree pane, select the file system.
4. On the Edit menu, select File System Configuration.
The File System Configuration wizard opens in edit mode.
5. Click Next until the Level 1 - Centera Backend panel appears.
File system table (Solaris only)
As root, edit the /etc/vfstab file so that the entry for the file system uses the bckendreten option, as shown here:
/blkdev /chardev /mntpnt utdm 2 yes fstype=fstype,bckendreten
Save the file and mount the file system:
mount /mntpnt File system table
(Linux and HP-UX only)
As root, edit the /etc/fstab file so that the entry for the file system uses the bckendreten option, as shown here:
/blkdev /mntpnt utdm fstype=fstype,bckendreten 0 2 Save the file and mount the file system:
mount /mntpnt File system table
(AIX only)
As root, edit the /etc/filesystems file so that the options line of the file system’s entry includes the bckendreten option:
options=rw,fstype=fstype,log=/dev/log,bckendreten Save the file and mount the file system:
mount /mntpnt
Table 33 Mounting with EMC Centera data retention (page 2 of 2) Mounting method Procedure
6. In Retention Class, type the name of an EMC Centera retention class.
Note:If a suitable retention class does not exist on the EMC Centera, you can specify a retention period. However, Retention Period cannot be Noneif Retention Class is empty.
7. Click Next until the Finish and Commit panel appears.
8. Click Finish.
The configuration is validated, saved, and committed. The file system is ready to use and EMC Centera data retention is active.
Note:Steps 1 through 8 describe how to edit an existing file system configuration to set EMC Centera data retention. You may edit other file system configuration parameters when performing these steps. You can also set EMC Centera data retention when a file system is first configured.
Setting retention for a group of files
To set EMC Centera data retention for a group of files in a file system:
1. Mount the file system by using the bckendreten mount option.
“Enabling EMC Centera data retention” on page 111provides more information.
2. Start Console Client and log in to the management domain that controls the file system’s FSM host.
“How to start Console Client” on page 24describes how to start Console Client and log in to a management domain.
3. On the tree pane, select the file system.
4. On the View menu, select Extended Rules.
5. On the Extended Rules tab, click Create New Rule.
The Extended Rule wizard appears.
6. In Rule Name, type a name for the new rule.
The name may be any combination of ASCII characters, from 1 to 32 characters in length. The name cannot match the name of any other extended rule in the file system.
7. Form a match string that identifies the group of files.
“Creating an extended rule” on page 74provides information about forming a match string.
8. Click Next until the Centera Actions panel for the primary back-end system appears.
9. In Retention Class, type the name of a valid EMC Centera retention class.
Note:If a suitable retention class does not exist on the EMC Centera, you can specify a retention period. However, Retention Period cannot be Noneif Retention Class is empty.
10. Click Next until the Finish and Commit panel appears.
11. Click Finish.
The extended rule is validated, saved, and committed. The file system is ready to use and EMC Centera data retention is active for the specified group of files.
Note:Steps 1 through 11 describe how to create an extended rule to set EMC Centera data retention for a group of files. You may specify other extended rule parameters when performing these steps. You can also edit an existing extended rule to add EMC Centera data retention.
Restoring incremental backups
EMC Centera data retention can prevent the use of incremental backups to restore some files to a UTDM file system. The affected files are those that have all of the following characteristics:
◆ The file is not a migration candidate when the full backup is created.
◆ The file is modified after the full backup is created and before incremental backup is created.
◆ The time between the creation of the full backup and the restoring of the incremental backup is greater than the value of the Delay Until Migrate Candidacy value.
When all of these characteristics are true for a file, the UTDM file system allows the restore of the file from the full backup, but rejects the restore of the file from the incremental backup.
To restore incremental backups while using EMC Centera data retention:
1. Start Console Client and log in to the management domain that controls the file system’s FSM host.
“How to start Console Client” on page 24describes how to start Console Client and log in to a management domain.
2. On the tree pane, select the file system.
3. On the Edit menu, select File System Configuration.
The File System Configuration wizard opens in edit mode.
Attributes that cannot be edited are unavailable.
4. Click Next until the Optional Migration Settings panel appears.
5. Increase the value of Delay Until Migrate Candidacy.
The value of Delay Until Migrate Candidacy is expressed in minutes. It must be increased to be greater than the number of minutes from the time of the full backup to the time of the restore.
6. Click Next until the Finish and Commit panel appears.
7. Click Finish.
The edited configuration is validated, saved, and committed.
8. Perform a restore by using the incremental backup.
9. Change Delay Until Migrate Candidacy back to its original value.
Restore of the incremental backup is complete.