ZFS Device Replacement Enhancements

Oracle Solaris 10 9/10 Release: In this Solaris release, a system event or sysevent is provided when an a disk is replaced with larger disk or the disks in the pool are replaced with larger disks. ZFS has been enhanced to recognize these events and adjusts the pool based on the new size of the disk, depending on the setting of the autoexpand property. You can use the autoexpand pool property to enable or disable automatic pool expansion when a larger disk replaces a smaller disk.

These features enable you to increase the pool sizewithout having to export and import pool or reboot the system.

For example, the autoexpand property isenabled on the tank pool.

# zpool set autoexpand=on tank

Or, you can create the pool with the autoexpand property enabled.

# zpool create -o autoexpand=on tank c1t13d0

The autoexpand property is disabled by default so you can decide whether you want the pool size expanded when a larger disk replaces a smaller disk.

The pool size also be expanded by using the zpool online -e command. For example:

# zpool online -e tank c1t6d0

Or, you can reset the autoexpand property after the larger disk is attached or made available by using the zpool replace feature. For example, the following pool is created with one 8-GB disk (c0t0d0). The 8-GB disk is replaced with a 16-GB disk (c1t13d0), but the pool size is not expanded until the autoexpand property is enabled.

# zpool create pool c0t0d0
# zpool list
NAME   SIZE   ALLOC  FREE    CAP   HEALTH  ALTROOT
pool   8.44G  76.5K  8.44G     0%  ONLINE  -
# zpool replace pool c0t0d0 c1t13d0
# zpool list
NAME   SIZE   ALLOC  FREE    CAP   HEALTH  ALTROOT
pool   8.44G  91.5K  8.44G     0%  ONLINE  -
# zpool set autoexpand=on pool
# zpool list
NAME   SIZE   ALLOC  FREE    CAP   HEALTH  ALTROOT
pool   16.8G   91.5K  16.8G    0%  ONLINE  -

Another way to expand the LUN in the above example without enabling the autoexpand property, is to use the zpool online -e command even though the device is already online. For example:

# zpool create tank c0t0d0
# zpool list tank
NAME   SIZE   ALLOC  FREE    CAP   HEALTH  ALTROOT
tank   8.44G  76.5K  8.44G     0%  ONLINE  -
# zpool replace tank c0t0d0 c1t13d0
# zpool list tank
NAME   SIZE   ALLOC  FREE    CAP   HEALTH  ALTROOT
tank   8.44G  91.5K  8.44G     0%  ONLINE  -
# zpool online -e tank c1t13d0
# zpool list tank
NAME   SIZE   ALLOC  FREE    CAP   HEALTH  ALTROOT
tank   16.8G    90K  16.8G     0%  ONLINE  -

Additional device replacement enhancements in this release include the following features:

• In previous releases, ZFS was not able to replace an existing disk with another disk or attach a disk if the replacement disk was a slightly different size. In this release, you can replace an existing disk with another disk or attach a new disk that is nominally the same size provided that the pool is not already full.

• In this release, you do not need to reboot the system or export and import a pool to expand the pool size. As described above, you can enable the autoexpand property or use the zpool online -e command to expand the pool size.

For more information about replacing devices, see Replacing Devices in a Storage Pool.