Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 129)

Changing An Existing Configuration by Migrating
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Changing RAID Level
You can use migrate to change the RAID level of an existing unit while the
unit is online, without experiencing any data loss. When you change a RAID
level, you may also add one or more drives to the unit. You can also migrate to
change the unit's stripe size. For example, a four-drive RAID 5 with a 64KB
Table 10: Valid Migration Paths
Destination
Source R0 R1 R5 R6 R10 R50 Single Spare
R0 Yes No Yes Yes Yes Yes No No
R1 Yes No Yes Yes Yes Yes Yes No
R5 Yes No Yes Yes Yes Yes No No
R6 Yes No Yes Yes Yes Yes No No
R10
Yes No Yes Yes Yes Yes No No
R50 Yes No Yes Yes Yes Yes No No
Single Yes Yes Yes Yes Yes Yes No No
Spare No No No No No No No No
Note: Rapid RAID Recovery will be disabled on any unit that is migrated.
Warning: If you are booted from a mirror (RAID 1 unit), never split it into 2 single
(identical) drives. Once the unit is split, any pending writes cannot be written to the
second drive. In addition, the file system on the drive will not be clean. Instead, shut
down the system, replace one of the drives, and start the rebuild from 3BM.
Note: You can only migrate a unit to a RAID level that has the same or more
capacity as the existing one. A four-drive RAID 5 unit can migrate to a four-drive
RAID 0, but a three-drive RAID 0 unit cannot migrate to a three-drive RAID 5,
without adding another drive, due to the need for additional storage capacity for
parity bits.