Areca ARC-1110, Руководство пользователя

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INTRODUCTION
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1.3.3.4 Online RAID Level and Stripe Size Migration
For those who wish to later upgrade to any RAID capabilities, a
system with Areca online RAID level/stripe size migration allows
a simplified upgrade to any supported RAID level without having
to reinstall the operating system.
ARC-11xx/12xx can migrate both the RAID level and stripe size
of an existing volume set, while the server is online and the
volume set is in use. Online RAID level/stripe size migration
can prove helpful during performance tuning activities as well
as when additional physical disks are added to the SATA RAID
controller. For example, in a system using two drives in RAID
level 1, it is possible to add a single drive and add capacity and
retain fault tolerance. (Normally, expanding a RAID level 1 ar -
ray would require the addition of two disks). A third disk can be
added to the existing RAID logical drive and the array can then
be migrated from RAID level 1 to 5. The result would be parity
fault tolerance and double the available capacity without tak -
ing the system down. A forth disk could be added to migrate to
RAID level 6. It is only possible to migrate to a higher RAID level
by adding a disk; disks in an existing array can’t be reconfigured
for a higher RAID level without adding a disk.
Online migration is only permitted to begin If all volume to be
migrated are in the normal mode. During the migration pro -
cess, the volume sets being migrated are accessed by the host
system. In addition, the volume sets with RAID levels 1, 1E,
3, 5 or 6 are protected against data loss in the event of disk
failure(s). In the case of disk failure, the volume set transitions
from migrating state to (midegraded) state. When the
migration is completed, the volume set transitions to degraded
mode. If a global hot spare is present, then it further transitions
to rebuilding state.
1.3.3.5 Online Volume Expansion
Performing a volume expansion on the controller is the process
of growing only the size of the lastest volume. A more flexible
option is for the array to concatenate an additional drive into the
RAID set and then expand the volumes on the fly. This happens