Compaq HSZ80 manual Initialize Switches, Chunk Size

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Initialize Switches

You can enable the following kinds of switches to affect the format of a disk drive or storageset:

■Chunk size (for stripesets and RAIDsets only)

■Save configuration

■Destroy/Nodestroy

After you initialize the storageset or disk drive, you cannot change these switches without reinitializing the storageset or disk drive.

Chunk Size

Specify a chunk size to control the stripesize used for RAIDsets and stripesets:

■CHUNKSIZE=DEFAULT lets the controller set the chunk size based on the number of disk drives (d) in a stripeset or RAIDset. If d < 9, then chunk size = 256. If d > 9, then chunk size = 128.

■CHUNKSIZE=n lets you specify a chunk size in blocks. The relationship between chunk size and request size determines whether striping increases the request rate or the data-transfer rate.

IMPORTANT: While a storageset may be initialized with a user-selected chunk size, it is recommended that only the default value be used. The default value is chosen to produce optimal performance for a wide variety of loads. The use of a chunk size less than 128 blocks (64K) is strongly discouraged. There are almost no customer loads for which small chunk sizes are of value and, in almost all cases, selecting a small chunk size will severely degrade the performance of the storageset and the controller as a whole. Use of a small chunk size on any storageset can result in severe degradation of overall system performance.

Compaq HSZ80 Array Controller ACS Version 8.3 Configuration and CLI Reference Guide