Data Storage 101
In this guide, we will explain the differences between:
» DAS (Direct Attached Storage)
» JBOD (Just a Bunch Of Drives)
» NAS (Network Attached Storage)
» SAN (Storage Area Network)
» NAS vs SAN
» Storage Servers
» Storage Virtualization
» SDS (Software Defined Storage)
» Free storage software
DAS (Direct Attached Storage)
Direct Attached Storage (DAS), also called Direct Attach Storage, is digital storage that is attached directly to a PC or a server. In other words, DAS isn't part of a storage network.
The most familiar example of DAS is the internal hard drive in a laptop or desktop PC.
In practice, the term "direct attached storage" is used most often in reference to dedicated storage arrays attached directly to servers.
It is used to distinguish DAS from networked storage arrangements, like SAN or NAS devices.
DAS (Direct Attached Storage) – cont.
DAS can refer to a single drive or a group of drives that are connected together, as in a RAID array.
In addition, DAS devices can be housed inside a PC or server (as is the case with internal hard drives) or outside the PC or server (as is the case with external hard drives and JBOD’s).
The primary benefits of DAS include simplicity and low cost.
Most PCs and servers come with DAS already installed and if you want to add more direct attached storage, generally all you need to purchase is a storage device and possibly a cable.
DAS (Direct Attached Storage) – cont.
Installing networked storage systems, like NAS and SAN devices,
requires additional planning, as well as the purchase and deployment of network hardware, such as routers and switches, in addition to
appropriate cabling and connections.
Maintaining DAS is very simple; by contrast, SAN and NAS solutions usually require management software and may require monitoring software as well.
JBOD (Just a Bunch Of Drives)
JBOD (an acronym for "just a bunch of disks," or sometimes "just a bunch of drives") is an array of hard disks that haven't been configured.
A JBOD chassis presents the individual disks (to a server) with no structure applied.
The drives can be used as individual logical volumes or configured as a RAID using a RAID card or software.
NAS (Network Attached Storage)
A NAS is a server connected to the local area network that is dedicated to nothing more than file sharing.
NAS allows more storage space to be added to a network without affecting any systems already on the network.
With a NAS device, storage does not need to be an integral part of the desktop/workstation/server. Instead, the desktop/workstation/server still handles all of the processing of data but a NAS device delivers the data to the user.
NAS (Network Attached Storage) – cont.
A NAS device can exist anywhere in a network and many can be added to the network infrastructure.
The advantage of NAS over DAS is that it simplifies file sharing among multiple users.
SAN (Storage Area Network) – cont.
A SAN is a high-speed network of storage devices, separate from the local area network, that also connects those storage devices with
servers.
It provides block-level storage that can be accessed by the applications running on any and all servers connected to the SAN.
SAN storage devices can include tape libraries, and, more commonly, disk-based devices, like RAID hardware.
NAS vs SAN
It is easy to confuse the two, but SAN (storage area network) is an actual network, while NAS (network-attached storage) refers to a storage device, typically in an IP (LAN) network.
While a SAN provides block-level storage for servers, a NAS device provides file-level storage for end users.
The mail application on company servers might utilize a SAN to store all the messages, contacts and other data it requires.
An end user would use a NAS device to save files, such as word processing documents or spreadsheets.
NAS vs SAN – (cont.)
NAS is a much simpler and less expensive technology.
Using NAS devices actually simplifies the task of adding storage to a network because the NAS eliminates the need to configure a network operating system for routine file-sharing tasks.
A storage area network is designed for managing very large amounts of network storage.
For large organizations with many servers that need access to the same data, SAN offers better performance and flexibility than DAS or NAS.
NAS vs SAN – Summary
» Intel® Xeon® E5-2600 v3 processors
» NAS devices offer a simple, inexpensive way to get shared file-based storage.
» NAS works across the network while SAN doesn’t. While SAN
volumes can be mapped across the network, the file sharing on a NAS is much simpler.
» NAS can be accessed across multiple operating systems but not SAN. Windows, Linux and Mac OS can easily see files on a NAS.
NAS vs SAN – Summary (cont.)
» NAS backups are more efficient than SAN backups. This is because the files themselves are backed up instead of all of the blocks on the disk.
» For maximum performance, SANs provide a stronger information infrastructure foundation.
» There are other hybrid options available, such as iSCSI SANs, which offer some of the best features of both worlds.
Storage Servers
A storage server is a network server that is dedicated to managing storage. A network attached storage (NAS) device is a true storage
server because it is dedicated to data access and nothing else. This is in contrast to a file server, database server or video server which perform other functions besides managing storage. Storage servers tend to run an operating system tailored to the task of managing large amounts of storage.
Storage Virtualization
Storage virtualization is the pooling of physical storage from multiple network storage devices into what appears to be a single storage
device that is managed from a central console.
Storage virtualization helps the storage administrator perform the tasks of backup, archiving and recovery more easily -- and in less time -- by disguising the actual complexity of a SAN or cluster of NAS
devices.
Administrators can implement virtualization with software
SDS (Software Defined Storage)
SDS is a storage infrastructure that is managed and automated by software as opposed to by the storage hardware itself.
It can be thought of as a software layer that provides storage services.
In this way, the pooled storage resources in an SDS environment can be automatically and efficiently allocated to match the needs of any application.
SDS (Software Defined Storage) – cont.
The key benefits of software-defined storage over traditional storage are increased flexibility, automated management and cost efficiency. The downside to SDS is that the server has to allocate greater
resources to manage the storage. Functions that were done in dedicated hardware on traditional storage systems now has to be done by the server CPU. This can impact the speed and
responsiveness of other applications running on the server.
Free Storage Software
Eventually, you will hear the old adage “Hey, I read about this free software, such as FreeNAS, NAS4free, OpenFiler, etc. Why can’t I use that?”
While it may be free to acquire the software, most have the
limitation of being NAS based. Maximum available storage, security and data integrity may also be limited. Setting up and maintaining the system can be time consuming and require significant technical skills. They may end up costing more in the long run than purchasing
Summary
» The types of storage used depends on the needs of the customer.
» Separate desktops/workstations/servers can use DAS if no other systems need access to the data.
» NAS can be used for simple file sharing.
» SAN is used when multiple servers need access to the same data (ex: databases).
