Understanding RAID Levels

> Understanding RAID Levels

> RAID stands for Redundant Array of Independent Disks. When you create storage configurations you can use several different types of RAID technology, called RAID levels, to create multiple drives, or drive groups, on which to store data. The computer operating system sees each drive group as a single virtual drive, not as a collection of individual drives.

> | A RAID 0 drive group has two or more drives.

> Data is divided into small blocks (strips) that are written successively to all of the drives in the drive group. Thus, at the same time data block 1 is written to drive 1, data block 2 is being written to drive 2, and so on. This RAID level is obviously faster than writing an entire file to one drive, and reading files is faster as well. RAID 0 is a good choice if fast read/write capability is the most important objective. However, RAID 0 drive groups are not fault tolerant and cannot be protected with hot spare drives.

> | A RAID 1 drive group has two drives.

> Data is written simultaneously to both drives, so that one drive is a mirror of the other. If one of the drives fails, the data is still protected. You can use a hot spare drive to automatically replace a failed mirrored drive. RAID 1 provides a high level of data protection. However, data writes are slower than with a RAID 0 drive group because all data must always be written to two drives. Also, the two-drive RAID 0 drive group has only one drive of actual capacity.

> | A RAID 1E drive group is the same as a RAID 0 drive group, except that the data is divided into strips, and each strip is then written to one drive and mirrored on another drive.

> Thus, the data is protected by the mirroring arrangement. As with RAID 1, if a drive in the drive group fails, a hot spare drive can automatically replace it. RAID 1E performance is roughly the same as for a single drive, although in some instance the dual write which might be somewhat slower.

> | A RAID 10 drive group is a spanned drive group that creates a striped set from a series of mirrored drives.

> The drive group can sustain multiple drive losses as long as no two drives lost comprise a single pair of one mirror.

> NOTE The IT controller does not support RAID. All references to virtual drives and RAID actions do not apply to IT controllers.

> NOTE Integrated RAID 1 supports RAID 0, RAID 1, and RAID 1E. Integrated RAID 2 and Integrated RAID 3 support RAID 0, RAID 1, RAID 1E, and RAID 10.

> NOTE RAID 1E and RAID 10 support and display depends on Manufacturing Page 10 of the Integrated RAID 2 and Integrated RAID 3 Firmware.

DB09000202-21, Rev 2.2, July 2015
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