Promise Technology VTrak 15110 - Manual (Page 225)

Chapter 7: Technology Background
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Choosing Stripe Block Size
The stripe block size value can be set to 4KB, 8KB, 16KB, 32KB, and 64KB.
64 KB is the default. This selection will directly affect performance. There are two
issues to consider when selecting the stripe block size.
•
Choose a stripe block size equal to or smaller than the smallest cache buffer
found on any disk drive in your disk array. A larger value slows the disk array
down because disk drives with smaller cache buffers need more time for
multiple accesses to fill their buffers.
• If your data retrieval consists of fixed-size data blocks, such as some
database and video applications, choose that data block size as your stripe
block size.
Generally speaking, email, POS and webservers prefer smaller stripe block
sizes. Video and database applications prefer larger stripe block sizes.
Gigabyte Boundary
The Gigabyte Boundary feature is designed for disk arrays in which a drive has
failed and the user cannot replace the drive with the same capacity or larger.
Instead, the Gigabyte Boundary feature permits the installation of a replacement
drive that is slightly smaller (within 1 gigabyte) than the remaining working drive
(for example, an 80.5GB drive would be rounded down to 80GB). This can be
helpful in the event that a drive fails and an exact replacement model is no longer
available. With VTrak, this feature is always enabled.
Initialization
Initialization is the process of setting all of the data bits on all of the disk drives to
zero. This has the effect of erasing any existing data from the drives. This action
is especially helpful in creating accurate parity in disk arrays with more than four
drives.
Initialization applies to RAID 1, 3, 5, 10 and 50. If you create one of these disk
arrays automatically, the disk array is always initialized. If you create the disk
array manually, you can choose whether to initialize.
The initialization process begins immediately after the disk array is created and
may take some time to finish, depending on the size of the disk drives in your disk
array. Your disk array is available while initialization is in progress.