Users guide

Intel® RAID Software User Guide 8
1.3.3.1 Disk Striping
Disk striping writes data across all of the physical disks in the array into fixed size
partitions or stripes. In most cases, the stripe size is user-defined. Stripes do not provide
redundancy but improve performance since striping allows multiple physical drives to be
accessed at the same time. These stripes are interleaved in a repeated sequential manner
and the controller knows where data is stored. The same stripe size should be kept across
RAID arrays.
Terms used with strip sizing are listed below:
• Strip size: One disk section
• Stripe size: Total of one set of strips across all data disks, not including parity
stripes
• Stripe width: The number of disks involved
1.3.3.2 Disk Spanning
Disk spanning allows more than one array to be combined into a single virtual drive. The
spanned arrays must have the same stripe size and must be contiguous. Spanning alone
does not provide redundancy but RAID modes 10, 50, and 60 all have redundancy
provided in their pre-spanned arrays through RAID 1, 5, or 6.
Note: Sp
anning two contiguous RAID 0 drives does not produce a new RAID level or add fault
tolerance. It does increase the size of the virtual volume and improves performance by
doubling the number of spindles. Spanning for RAID 10, RAID 50, and RAID 60 requires
two to eight arrays of RAID 1, 5, or 6 with the same stripe size and that always uses the
entire drive.
1.3.3.3 CPU Usage
Resource allocation provides the user with the option to set the amount of compute cycles
to devote to various tasks, including the rate of rebuilds, initialization, consistency checks,
and patrol read. Setting resource to 100% gives total priority to the rebuild. Setting it at
0% means the rebuild will only occur if the system is not doing anything else. The default
rebuild rate is 30%.