HP D5970A - NetServer - LCII Installation And Configuration Manual page 49

Chapter 4

Logical Drive Size
You can calculate the usable capacity to assign to each logical drive, or you can
let the HP NetRAID Assistant Wizard specify it during configuration. If you
calculate logical drive capacity, record it in Worksheet B.
If you want a logical drive to occupy less space than is available on one array,
you must enter the logical drive size.

Stripe Size (Stripe Depth)
Stripe size is the amount of data contiguously written to each disk in an array. It
is sometimes called "stripe depth." You can specify stripe sizes of 4 KB, 8 KB,
16 KB, 32 KB, 64 KB, and 128 KB for each logical drive. Consider the following
when setting your stripe size:
The default stripe size is 8 KB.
A stripe size of 128 KB requires at least 8 MB of memory.
For best performance, choose a stripe size equal to or smaller than the
block size used by your operating system.
A large stripe size produces better performance if the system does mostly
sequential reads.
Choose a small stripe size if your system performs mostly random reads.
Online conversions of RAID 3 logical drives can be done only if the stripe
size is 64 KB.
For each logical drive, log the stripe size in Worksheet B.
NOTE

Write Policy
When the IOP writes to disk, the data is first written to the cache on the
assumption that the IOP will read it again soon. The two Write policies are:
Write-Through: In a write-through cache, data is written to disk at the
same time it is cached. This setting provides better security because
entries are always copied to disk. If no Uninterruptible Power Supply (like
HP NetRAID's Battery Backup unit) is connected, you should use the
write-through setting, because otherwise data could be lost from cache
memory in a power failure.
Consider the stripe size carefully, because once configured,
you cannot change the size.
Planning
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