Learning About Custom Configuration - IBM Netfinity ServeRAID-3H Installation And User Manual

Learning about Custom configuration

The Custom configuration path allows you to manually configure your ServeRAID subsystem. Using this
path, you can select the drives that you want to include in each array, define the number and size of the
logical drives for each array, and select the drives that you want to use as hot spares.
Before you select the Custom configuration path, consider the following:
If you are not familiar with the IBM implementation of RAID technology, you might want to review the
information provided in "Understanding RAID technology" on page 4 before you begin.
Each ServeRAID controller supports a maximum of eight arrays.
Each ServeRAID controller supports a maximum of eight logical drives.
When you create an array, you group physical drives into one storage area. You can define this
storage area as a single logical drive, or you can subdivide it into several logical drives. Each logical
drive appears to the operating system as a single physical drive.
If you have only one array, you can define it as a single logical drive, or you can divide it into several
logical drives. Typically, the first logical drive defined on the first ServeRAID controller found by the
basic input/output system (BIOS) during startup will be your startup (boot) drive.
If you have two or more arrays, each array can be one logical drive, or you can divide each array into
multiple logical drives, as long as the total number of logical drives for all of the arrays does not
exceed eight.
Note: Independent of the RAID logical drives, most operating systems allow you to partition the
logical drives further.
The optimal way to create arrays is to use physical drives that have the same capacity.
Physical drive capacities influence the way you create arrays. Drives in an array can be of different
capacities (1 GB 6 , or 2 GB, for example), but RAID controllers treat them as if they all have the
capacity of the smallest disk drive.
For example, if you group three 1 GB drives and one 2 GB drive into an array, the total capacity of the
array is 1 GB times 4, or 4 GB, not the 5 GB physically available. Similarly, if you group three 2 GB
drives and one 1 GB drive into an array, the total capacity of that array is 4 GB, not the 7 GB
physically available.
A hot-spare drive is a disk drive that is defined for automatic use in the event of a drive failure. The
hot-spare drive must be of equal or greater capacity than the drive that it is intended to replace. If a
physical drive fails and it is part of a RAID level-1, RAID level-1E, RAID level-5, or RAID level-5E
logical drive, the ServeRAID controller automatically starts to rebuild the data on the hot-spare drive.
If you are using the ServeRAID-3L:
– Eight physical drives are supported in an array if the stripe-unit size is set to 32 KB or 64 KB.
– Sixteen physical drives are supported in an array if the stripe-unit size is set to 8 KB or 16 KB.
If you are using the ServeRAID-3H or ServeRAID-3HB, sixteen physical drives are supported in an
array if the stripe-unit size is set to 32 KB or 64 KB. (See "Stripe-unit size" on page 4 for more
information.)
6 When referring to hard-disk-drive capacity, GB means approximately 1 000 000 000 bytes; total user-accessible capacity may vary
depending on operating environment.
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IBM ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L, Controllers