GPFS: Administration and Programming Reference - IRA Home

Deleting disks from a file system
Before deleting a disk use the mmdf command to determine whether there is enough free space on the
remaining disks to store the file system. See “Querying file system space” on page 21. Consider how
fragmentation may increase your storage requirements, especially when the file system contains a large
number of small files. A margin of 150 percent of the size of the disks being deleted should be sufficient to
allow for fragmentation when small files predominate. For example, in order to delete a 4 GB disk from
your file system, which contains user home directories with small files, you should first determine that the
other disks in the file system contain a total of 6 GB of free space.
If you do not replicate your file system data, you should rebalance the file system using the mmrestripefs
-b command. If you replicate your file system data, run the mmrestripefs -r command after the disk has
been deleted. This ensures that all data will still exist with correct replication after the disk is deleted. The
mmdeldisk command only migrates data that would otherwise be lost, not data that will be left in a single
copy.
Note: Rebalancing of files is an I/O intensive and time consuming operation, and is important only for file
systems with large files that are mostly invariant. In many cases, normal file update and creation
will rebalance your file system over time, without the cost of the rebalancing.
Do not delete stopped disks, if at all possible. Start any stopped disk before attempting to delete it from
the file system. If the disk cannot be started you will have to consider it permanently damaged. You will
need to delete the disk using the appropriate options. If metadata was stored on the disk, you will need to
execute the offline version of the mmfsck command. See the General Parallel File System: Problem
Determination Guide and search for NSD failures for further information on handling this.
When deleting disks from a file system, the disks may or may not be available. If the disks being deleted
are still available, GPFS moves all of the data from those disks to the disks remaining in the file system.
However, if the disks being deleted are damaged, either partially or permanently, it is not possible to move
all of the data and you will receive I/O errors during the deletion process. For instructions on how to
handle damaged disks, see the General Parallel File System: Problem Determination Guide and search for
Disk media failure.
Specify the file system and the names of one or more disks to delete with the mmdeldisk command. For
example, to delete the disk hd2n97 from the file system fs1 enter:
mmdeldisk fs2 hd2n97
The system displays information similar to:
Deleting disks ...
Scanning ’system’ storage pool
Scanning file system metadata, phase 1 ...
11 % complete on Fri Feb 3 16:01:36 2006
31 % complete on Fri Feb 3 16:01:42 2006
86 % complete on Fri Feb 3 16:01:58 2006
100 % complete on Fri Feb 3 16:02:01 2006
Scan completed successfully.
Scanning file system metadata, phase 2 ...
40 % complete on Fri Feb 3 16:02:04 2006
100 % complete on Fri Feb 3 16:02:08 2006
Scan completed successfully.
Scanning file system metadata, phase 3 ...
9 % complete on Fri Feb 3 16:02:11 2006
42 % complete on Fri Feb 3 16:02:18 2006
100 % complete on Fri Feb 3 16:02:22 2006
Scan completed successfully.
Scanning file system metadata, phase 4 ...
Scan completed successfully.
Scanning user file metadata ...
1 % complete on Fri Feb 3 16:02:32 2006
Chapter 4. Managing disks 29