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
stripe size can be migrated to a four-drive RAID 5 with 256KB stripe size.
The steps below describe how to change a RAID level in 3DM2.
Single
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
JBOD
No
No
No
No
No
No
No
No
No
Spare
No
No
No
No
No
No
No
No
No
Table 10: Valid Migration Paths
Destination
Source
R0
R1
R5 R6
R10
R50
Single
JBOD
Spare
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.
Note:
Once migration starts, the unit stays in the migrating state until the migration
process is complete. The migration process cannot be aborted, and must be
allowed to finish before a rebuild or verify to the unit is permitted.
Warning:
It is important that you allow migration to complete before removing any
drives that are involved in the migration. Removing drives from the unit during
migration may cause the migration process to stop, and can jeopardize the safety of
your data.
