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). 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 4GB 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 6GB of free space.
If you do not replicate your file system data, you should suspend the disk you intend to delete and then rereplicate the file system using the mmrestripefs -r command. If you replicate your file system data, run mmrestripefs -r after the disk has been deleted. This insures 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.
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 off-line version of the mmfsck command. See the IBM General Parallel File System for AIX: Problem Determination Guide and search for disk failures for further information on handling this.
If you detect a faulty disk, or decide to move disk resources out of the GPFS file system, you can delete a disk from a previously defined file system. 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. The options you may use to continue processing in the event the disks are damaged, are:
This option is valid only for a file system where replication has been set for metadata (see the mmcrfs and the mmchfs commands). Any subsequent request to read data from a file that was stored on a deleted disk and not sufficiently replicated returns an I/O error (EIO).
Specify the file system and the names of one or more disks to delete, along with any instructions about how to handle the disk data, with the mmdeldisk command. For example, to delete the disk gpfs7vsd from the file system fs1, and rebalance the files across the remaining disks, enter:
mmdeldisk fs1 gpfs7vsd -r
The system displays information similar to:
(16:02:42) k145n02:/ # mmdeldisk fs1 gpfs7vsd -r Deleting disks ... GPFS: 6027-589 Scanning file system metadata, phase 1 ... GPFS: 6027-552 Scan completed successfully. GPFS: 6027-589 Scanning file system metadata, phase 2 ... GPFS: 6027-552 Scan completed successfully. GPFS: 6027-589 Scanning file system metadata, phase 3 ... GPFS: 6027-552 Scan completed successfully. GPFS: 6027-565 Scanning user file metadata ... 6 % complete on Wed Aug 16 16:03:25 2000 100 % complete on Wed Aug 16 16:03:27 2000 GPFS: 6027-552 Scan completed successfully. GPFS: 6027-370 tsdeldisk completed. mmdeldisk: 6027-1371 Propagating the changes to all affected nodes. This is an asynchronous process. Restriping fs1 ... GPFS: 6027-589 Scanning file system metadata, phase 1 ... 76 % complete on Wed Aug 16 16:03:57 2000 100 % complete on Wed Aug 16 16:03:58 2000 GPFS: 6027-552 Scan completed successfully. GPFS: 6027-589 Scanning file system metadata, phase 2 ... GPFS: 6027-552 Scan completed successfully. GPFS: 6027-589 Scanning file system metadata, phase 3 ... GPFS: 6027-552 Scan completed successfully. GPFS: 6027-565 Scanning user file metadata ... 6 % complete on Wed Aug 16 16:04:09 2000 100 % complete on Wed Aug 16 16:04:11 2000 GPFS: 6027-552 Scan completed successfully. Done
Refer to mmdeldisk Command for syntax and usage information.