Users Guide

Table 19. RAID 10 configurations (continued)
Disk or span
count
RAID 10
capable
Disk or span
count
RAID 10
capable
Disk or span
count
RAID 10
capable
Disk or span
count
RAID 10
capable
60 (2) Yes 120 (4) Yes 180 (6) Yes 240 (8) Yes
62 No 122 No 182 (7) Yes - -
RAID terminology
Disk striping
Disk striping allows you to write data across multiple physical disks instead of just one physical disk. Disk striping involves
partitioning each physical disk storage space in stripes of the following sizes: 64 KB, 128 KB, 256 KB, 512 KB, and 1 MB. The
stripes are interleaved in a repeated sequential manner. The part of the stripe on a single physical disk is called a stripe element.
For example, in a four-disk system using only disk striping (used in RAID 0), segment 1 is written to disk 1, segment 2 is written
to disk 2, and so on. Disk striping enhances performance because multiple physical disks are accessed simultaneously, but disk
striping does not provide data redundancy.
Figure 21. Example of disk striping (RAID 0)
Disk mirroring
With mirroring (used in RAID 1), data written to one disk is simultaneously written to another disk. If one disk fails, the contents
of the other disk can be used to run the system and rebuild the failed physical disk. The primary advantage of disk mirroring is
that it provides complete data redundancy. Both disks contain the same data at all times. Either of the physical disks can act as
the operational physical disk.
Disk mirroring provides complete redundancy, but is an expensive option because each physical disk in the system must be
duplicated.
NOTE: Mirrored physical disks improve read performance by read load balance.
Figure 22. Example of Disk Mirroring (RAID 1)
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Appendix RAID description