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APPENDIX
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Online RAID Level and Stripe Size Migration
For those who wish to later upgrade to any RAID capabilities,
a system with online RAID level/stripe size migration allows a
simplified upgrade to any supported RAID level without having
to reinstall the operating system.
The RAID controllers can migrate both the RAID level and
stripe size of an existing volume set, while the server is on
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line and the volume set is in use. Online RAID level/stripe size
migration can prove helpful during performance tuning activi-
ties as well as when additional physical disks are added to the
RAID controller. For example, in a system using two drives in
RAID level 1, it is possible to add a single drive and add ca-
pacity and retain fault tolerance. (Normally, expanding a RAID
level 1 array would require the addition of two disks). A third
disk can be added to the existing RAID logical drive and the
volume set can then be migrated from RAID level 1 to 5. The
result would be parity fault tolerance and double the avail-
able capacity without taking 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 volumes to
be migrated are in the normal mode. During the migration
process, the volume sets being migrated are accessed by the
host system. In addition, the volume sets with RAID level 1,
1E, 10, 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
