Accusys ExaRAID GUI - Manual (Page 273)

Appendix
B-4
• Selective initialization method and mode
To initialize a logical disk, either data zeroing or background parity
regeneration can be used. The administrator can choose to execute the
background initialization for all logical disks simultaneously or one by one
sequentially. To avoid confusing the operating systems, the background
initialization will also clean up the data on the first few sectors to erase the
file system super blocks. To speed up the initialization, the administrator can
also choose to initialize the disk group and skip the initialization of logical
disks.
• Selective rebuild mode
The rebuild mode of a disk group determines the rebuilding order of logical
disks on the disk group. Three rebuild modes are available: parallel,
sequential, and prioritized, by which the rebuilding will be done
simultaneously for all logical disks, sequentially from the first to the last logical
disks, and sequentially according to the order specified by the
administrator, respectively.
• Flexible hot spare policy
Hot spare disks are standby disks that are used for replacing faulty disks by
rebuilding the data of the faulty disks. Spare disks can be configured as
local spare dedicated to specific disk group or global spare shared by all
disk groups. Users can also enable the auto-spare option to force the spare
disk returns to standby after the faulty disks are replaced by newer disks. This
helps to control the physical organization of hard disks in the chassis.
B.5 Dynamic Configuration Migration
Business and users’ needs are dynamic, and the storage systems are
required to be aligned dynamically with the business requirements. As a
result, the administrators need to reconfigure the storage from time to time.
The RAID controllers are equipped with extensive utilities for online migration
of the RAID configurations while retaining the system availability. Without the
online reconfiguration utilities, unwanted system downtime and efforts for
offline manual reconfiguration will stop the administrator from optimizing the
storage.
• Online disk group expansion
Expanding a disk group by adding hard disks to be its member disks
enlarges the usable capacity of a disk group, and more logical disks can be
created from the disk group. An administrator can start a disk group with
few hard disks and expand the disk group later if more capacity is needed.
The initial cost from disk purchase can be minimized while future expansion
is guaranteed.
• Online RAID level and stripe size migration
For performance tuning or adjusting the reliability level, the RAID level and
stripe size needs to be changed. To execute the online migration, the