IBM Netfinity ServeRAID-4H Ultra160, User Reference

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Stripe-unit size
With RAID technology, data is striped across an array of physical drives. This
data-distribution scheme complements the way the operating system requests data.
The granularity at which data is stored on one drive of the array before subsequent
data is stored on the next drive of the array is called the stripe-unit size.
You can control the stripe-unit size and maximize the performance of your
ServeRAID controller by setting a stripe-unit size to a value that is close to the size
of the system I/O requests. You can set the stripe-unit size to 8 KB, 16 KB, 32 KB,
or 64 KB. For example, performance in transaction-based environments, which
typically involve large blocks of data, might be optimal when the stripe-unit size is
set to 32 KB or 64 KB. However, performance in file and print environments, which
typically involve multiple small blocks of data, might be optimal when the stripe-unit
size is set to 8 KB or 16 KB.
The collection of stripe units, from the first drive of the array to the last drive of the
array, is called a stripe.
The ServeRAID-4H controller supports 16 physical drives in an array if the
stripe-unit size is set to 32 KB or 64 KB.
Supported RAID levels
Disk arrays are used to improve performance and reliability. The amount of
improvement depends on the application programs that you run on the server and
the RAID levels that you assign to the logical drives.
The ServeRAID controllers support RAID level-0, 1, 1E, 5, 5E, 00, 10, 1E0, and 50.
Understanding RAID level-0
RAID level-0 stripes the data across all the drives in the array. This offers
substantial speed enhancement, but provides no data redundancy. RAID level-0
provides the largest storage capacity of the RAID levels that are offered, because
no room is taken for redundant data or data-parity storage.
RAID level-0 requires a minimum of one drive and, depending upon the level of
firmware and the stripe-unit size, supports a maximum of 8 or 16 drives.
The following illustration shows an example of a RAID level-0 logical drive.
Start with two physical drives.
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IBM
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Netfinity
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User’s Reference: ServeRAID
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-4H Ultra160 SCSI Controller