Promise Technology ultratrak RM8000, Руководство пользователя

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UltraTrak SX4000, SX8000 & RM8000 User Manual
20
Gigabyte Boundary
The Gigabyte Boundary feature is designed for fault tolerant arrays (RAID 1, 0+1,
3, 5, 30, and 50) 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, a 20.5GB drive would be rounded
down to 20GB). This can be helpful in the event that a drive fails and an exact
replacement model is no longer available. Without this feature enabled, UltraTrak
will NOT permit the use of a replacement drive that is slightly smaller than the
remaining working drive.
For the Gigabyte Boundary feature to work, the Gigabyte Boundary feature must
be set to ON when the original array is created. When enabled, the Gigabyte
Boundary feature rounds the drive capacity of all drives to the common whole GB
drive size. For example, with the Gigabyte Boundary feature enabled, the
remaining working drives can be 20.5GB and the replacement drive can be 20.3,
since all are rounded down to 20GB. This permits the smaller drive to be used.
Please note that users will lose a small amount of available storage capacity from
each drives in order to arrive at a common drive size.
Choosing Stripe Block Size
There are two issues to consider when selecting the Stripe Block Size.
First, you should choose a Stripe Block Size equal-to or smaller than the smallest
cache buffer found on any array disk drive. Selecting a larger value slows the
array down because disk drives with smaller cache buffers need more time for
multiple accesses to fill their buffers.
Secondly, if your data retrieval consists of fixed data blocks, such as with some
database or video applications – then you should choose that size as your Stripe
Block Size.