Adding disks to a file system
GPFS V3.1 Administration and Programming Reference
SA23-2221-00
Many files grow rapidly and you may decide that more disk space is required for your file system soon after creation. Before adding disks, see General Parallel File System: Concepts, Planning, and Installation Guide for details on creating disk descriptors.
To add disks to a GPFS file system, you first must decide if you will:
1. Create new disks using the mmcrnsd command.
You should also decide whether to use the rewritten disk descriptor file produced by the mmcrnsd command, or create a new list of disk descriptors. When using the rewritten file, the Disk Usage and Failure Group specifications remain the same as specified on the mmcrnsd command.
2. Select disks no longer in use in any file system. Issue the mmlsnsd -F command to display the available disks.
The disk may then be added to the file system using the mmadddisk command.
For example, to add the disk gpfs2nsd to the file system fs2, have it join failure group 1 in the storage pool system, and rebalance the existing files to take advantage of the added space, enter:
mmadddisk fs2 gpfs2nsd::::1 -r
The system displays information similar to:
GPFS: 6027-531 The following disks of fs2 will be formatted on node k145n01:
gpfs2nsd: size 4390912 KB
Extending Allocation Map
GPFS: 6027-1503 Completed adding disks to file system fs2.
mmadddisk: 6027-1371 Propagating the changes to all affected nodes.
This is an asynchronous process.
Restriping fs2 ...
GPFS: 6027-589 Scanning file system metadata, phase 1 ...
70 % complete on Wed Aug 16 15:14:28 2000
100 % complete on Wed Aug 16 15:14:29 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 15:14:45 2000
100 % complete on Wed Aug 16 15:14:46 2000
GPFS: 6027-552 Scan completed successfully.
Done
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.
When using an IBM® eServer High Performance Switch (HPS) in your configuration, it is suggested you process your disks in two steps:
1. Create virtual shared disks on each physical disk with the mmcrvsd command.
2. Using the rewritten disk descriptors from the mmcrvsd command, create NSDs with the mmcrnsd command.