Learning about Custom Configuration

^{IBM-AUSTRIA - PC-HW-Support 30 Aug 1999}

Learning about Custom Configuration

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' 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 hard disk 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 hard disk 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 adapter or 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 hard disk drives that have the same capacity.
Hard disk drive capacities influence the way you create arrays. Drives in an array can be of different capacities (1 GB 1, 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 or RAID level-5 logical drive, the ServeRAID controller automatically starts to rebuild the data on the hot-spare drive.
You can include a maximum of 16 physical drives in an array when the stripe-unit size is set to 8KB (the default setting) or 16KB, and you can include a maximum of 8 physical drives in an array when the stripe-unit size is set to 32KB or 64KB. (See 'Interleave Depth and Stripe-Unit Size' and 'Menu Bar' for more information.)

1 When referring to hard-disk-drive capacity, GB means approximately 1000000000 bytes, total user-accessible capacity may vary depending on operating environment.

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