Tuesday, July 31, 2012

Managing ZFS Storage Pool Properties

You can use the zpool get command to display pool property information. For example:

# zpool get all u03
u03  size           68G         -
u03  capacity       0%          -
u03  altroot        -           default
u03  health         ONLINE      -
u03  guid           601891032394735745  default
u03  version        22          default
u03  bootfs         -           default
u03  delegation     on          default
u03  autoreplace    off         default
u03  cachefile      -           default
u03  failmode       wait        default
u03  listsnapshots  on          default
u03  autoexpand     off         default
u03  free           68.0G       -
u03  allocated      76.5K       -
Storage pool properties can be set with the zpool set command. For example:

# zpool set autoreplace=on mpool
# zpool get autoreplace mpool
mpool autoreplace  on       default
Table 4–1 ZFS Pool Property Descriptions
Property NameTypeDefault ValueDescription
allocated StringN/ARead-only value that identifies the amount of storage space within the pool that has been physically allocated.
altroot Stringoff Identifies an alternate root directory. If set, this directory is prepended to any mount points within the pool. This property can be used when you are examining an unknown pool, if the mount points cannot be trusted, or in an alternate boot environment, where the typical paths are not valid.
autoreplace Booleanoff Controls automatic device replacement. If set to off, device replacement must be initiated by using the zpool replace command. If set to on, any new device found in the same physical location as a device that previously belonged to the pool is automatically formatted and replaced. The property abbreviation is replace.
bootfs BooleanN/AIdentifies the default bootable dataset for the root pool. This property is typically set by the installation and upgrade programs.
cachefile StringN/AControls where pool configuration information is cached. All pools in the cache are automatically imported when the system boots. However, installation and clustering environments might require this information to be cached in a different location so that pools are not automatically imported. You can set this property to cache pool configuration information in a different location. This information can be imported later by using the zpool import -c command. For most ZFS configurations, this property is not used.
capacity NumberN/ARead-only value that identifies the percentage of pool space used.
The property abbreviation is cap.
delegation Booleanon Controls whether a nonprivileged user can be granted access permissions that are defined for a dataset. For more information, see Chapter 9, Oracle Solaris ZFS Delegated Administration.
failmode Stringwait Controls the system behavior if a catastrophic pool failure occurs. This condition is typically a result of a loss of connectivity to the underlying storage device or devices or a failure of all devices within the pool. The behavior of such an event is determined by one of the following values:
  • wait – Blocks all I/O requests to the pool until device connectivity is restored, and the errors are cleared by using the zpool clear command. In this state, I/O operations to the pool are blocked, but read operations might succeed. A pool remains in the wait state until the device issue is resolved.
  • continue – Returns an EIO error to any new write I/O requests, but allows reads to any of the remaining healthy devices. Any write requests that have yet to be committed to disk are blocked. After the device is reconnected or replaced, the errors must be cleared with the zpool clear command.
  • panic – Prints a message to the console and generates a system crash dump.
free StringN/ARead-only value that identifies the number of blocks within the pool that are not allocated.
guid StringN/ARead-only property that identifies the unique identifier for the pool.
health StringN/ARead-only property that identifies the current health of the pool, as either ONLINE, DEGRADED, FAULTED, OFFLINE, REMOVED, or UNAVAIL.
listsnapshots Stringon Controls whether snapshot information that is associated with this pool is displayed with the zfs list command. If this property is disabled, snapshot information can be displayed with the zfs list -t snapshot command.
size NumberN/ARead-only property that identifies the total size of the storage pool.
version NumberN/AIdentifies the current on-disk version of the pool. The preferred method of updating pools is with the zpool upgrade command, although this property can be used when a specific version is needed for backwards compatibility. This property can be set to any number between 1 and the current version reported by the zpool upgrade -v command.

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