Moving a Metadata/Journal Stripe Group

Metadata movement is performed on a LUN level, meaning you must specify the source LUN and the destination LUN. The new sndiskmove command that accomplishes metadata movement has two arguments: a source and destination LUN.

After movement is complete, the physical source disk can be removed.

Note: Although a stripe group can consist of multiple disks or LUNs, the sndiskmove command moves only a single disk or LUN. Consequently, references to “stripe group” in this section refer to a single disk or LUN when migrating metadata with sndiskmove.

Caution: The command, sndiskmove, only works on disks or LUNs of the same size. For instance, if the destination LUN is smaller than the source LUN, then the command fails. However, if the destination LUN is larger than the source, then the additional capacity is ignored.

Caution: The metadata/journal stripe group you want to move cannot contain data.

sndiskmove treats metadata and journal stripe groups the same way, so it doesn’t matter whether the stripe group you want to move is a metadata stripe group, a journal stripe group, or a combined metadata and journal stripe group. The only caveat is that stripe groups used for movement cannot contain data.

If you attempt to move a metadata/journal stripe group that contains data, data loss could occur.

Use the following procedure to move a metadata/journal stripe group from a source LUN to a destination LUN.

  1. Stop the File System Manager (FSM) for the file system.
  2. If your StorNext configuration includes a failover environment, you must shut down any standby FSMs that would start when you shut down the primary FSM. The movement procedure will not complete successfully unless all FSMs are shut down.

Caution: If you do not shut down standby FSMs, file system corruption or data loss could occur.

  1. (Optional) Run the cvfsck command on the file system. See Checking the File System.
  2. Run sndiskmove <source-LUN-label-name> <destination-LUN-label-name>

where <source-LUN-label-name> is the source stripe group from which the move starts, and destination-LUN-label-name is the destination stripe group to which you want to move data.

During the move process StorNext appends “.old” to the source stripe group name. This is to avoid confusion because the destination stripe group is given the same name as the original stripe group. Both stripe group names remain in the configuration file.

For example:

source-LUN-label-name (the original stripe group name) becomes source-LUN-label-name.old

destination-LUN-label-name (the new stripe group name) becomes source-LUN-label-name (the same name as the original stripe group)

Note: When you run sndiskmove, it could take a considerable amount of time to copy the data between disks, depending on disk size and performance.

  1. Only if your system includes a standby FSM: After you run sndiskmove, rescan the disks on the standby FSM’s host by running cvadmin -e 'disks refresh'. You must run cvadmin -e 'disks refresh' on all systems on which you have a configured FSM for the file system involved in the move.
  2. Restart the FSM.
  3. Only if your system includes a standby FSM: Restart the standby FSM.