Metadevice and Disk Space Expansion

DiskSuite enables you to expand a metadevice by adding additional slices.

Mounted or unmounted UFS file systems contained within a metadevice can be expanded without having to halt or back up your system. (Nevertheless, backing up your data is always a good idea.) After the metadevice is expanded, you grow the file system with the growfs(1M) command.

After a file system is expanded, it cannot be decreased. Decreasing the size of a file system is a UFS limitation.

Applications and databases using the raw metadevice must have their own method to "grow" the added space so that the application or database can recognize it. DiskSuite does not provide this capability.

You can expand the disk space in metadevices in the following ways:

1. Adding a slice to a stripe or concatenation.

2. Adding multiple slices to a stripe or concatenation.

3. Adding a slice or multiple slices to all submirrors of a mirror.

4. Adding one or more slices to a RAID5 device.

You can use either DiskSuite Tool or the command line interface to add a slice to an existing metadevice.

When using DiskSuite Tool to expand a metadevice that contains a UFS file system, the growfs(1M) command is run automatically. If you use the command line to expand the metadevice, you must manually run the growfs(1M) command.

The growfs(1M) Command

The growfs(1M) command expands a UFS file system without loss of service or data. H`owever, write-access to the metadevice is suspended while the growfs(1M) command is running. You can expand the file system to the size of the slice or the metadevice that contains the file system.

The file system can be expanded to use only part of the additional disk space by using the -s size option to the growfs(1M) command.

When expanding a mirror, space is added to the mirror's underlying submirrors. Likewise, when expanding a trans metadevice, space is added to the master device. The growfs(1M) command is then run on the mirror or the trans metadevice, respectively. The general rule is that space is added to the underlying devices(s), and the growfs(1M) command is run on the top-level device.