ZFS Property Enhancements

Solaris Express Community Edition, builds 96-128: The following ZFS file system enhancements are included in these releases.

• Setting ZFS Security Labels – The mlslabel property is a sensitivity label that determines if a dataset can be mounted in a Trusted Extensions labeled-zone. The default is none. The mlslabel property can be modified only when Trusted Extensions is enabled and only with the appropriate privilege.

• Setting ZFS file system properties at pool creation time – You can set ZFS file system properties when the pool is created. In the following example, compression is enabled on the ZFS file system that is created when the pool is created.

  # zpool create -O compression=on pool mirror c0t1d0 c0t2d0

• Setting cache properties on a ZFS file system – Two new ZFS file system properties are provided in that allow you to control what is cached in the primary cache (ARC) or the secondary cache (L2ARC). The cache properties are set as follows:

  • primarycache – Controls what is cached in the ARC.

  • secondarycache – Controls what is cached in the L2ARC.

  • Possible values for both properties – all, none, and metadata. If set to all, both user data and metadata are cached. If set to none, neither user data nor metadata is cached. If set to metadata, only metadata is cached. The default is all.

  You can set these properties on an existing file system or when the file system is created. For example:

  # zfs set primarycache=metadata tank/datab # zfs create -o primarycache=metadata tank/newdatab

  When set on existing file systems, only new I/O is cache based on the value of these properties.

  Some database environments might benefit from not caching user data. You will have determine if setting cache properties is appropriate for your environment.

• Space accounting properties – New read-only file system properties help you identify space usage for clones, file systems, and volumes, but not snapshots. The properties are as follows:

  • usedbychildren – Identifies the amount of space that is used by children of this dataset, which would be freed if all the dataset's children were destroyed. The property abbreviation is usedchild.

  • usedbydataset – Identifies the amount of space that is used by this dataset itself, which would be freed if the dataset was destroyed, after first destroying any snapshots and removing any refreservation. The property abbreviation is usedds.

  • usedbyrefreservation – Identifies the amount of space that is used by a refreservation set on this dataset, which would be freed if the refreservation was removed. The property abbreviation is usedrefreserv.

  • usedbysnapshots – Identifies the amount of space that is consumed by snapshots of this dataset. In particular, it is the amount of space that would be freed if all of this dataset's snapshots were destroyed. Note that this is not simply the sum of the snapshots' used properties, because space can be shared by multiple snapshots. The property abbreviation is usedsnap.

  These new properties break down the value of the used property into the various elements that consume space. In particular, the value of the used property breaks down as follows:

  used property = usedbychildren + usedbydataset + usedbyrefreservation + usedbysnapshots

  You can view these properties by using the zfs list -o space command. For example:

  $ zfs list -o space NAME AVAIL USED USEDSNAP USEDDS USEDREFRESERV USEDCHILD rpool 25.4G 7.79G 0 64K 0 7.79G rpool/ROOT 25.4G 6.29G 0 18K 0 6.29G rpool/ROOT/snv_98 25.4G 6.29G 0 6.29G 0 0 rpool/dump 25.4G 1.00G 0 1.00G 0 0 rpool/export 25.4G 38K 0 20K 0 18K rpool/export/home 25.4G 18K 0 18K 0 0 rpool/swap 25.8G 512M 0 111M 401M 0

  The above command is equivalent to the zfs list -o name,avail,used,usedsnap,usedds,usedrefreserv,usedchild -t filesystem,volume command.

• Listing snapshots – The listsnapshots pool property controls whether snapshot information is displayed by the zfs list command. The default value is off, which means snapshot information is not displayed by default.

  You can use the zfs list -t snapshots command to display snapshot information. For example:

  # zfs list -t snapshot NAME USED AVAIL REFER MOUNTPOINT pool/home@today 16K - 22K - pool/home/user1@today 0 - 18K - pool/home/user2@today 0 - 18K - pool/home/user3@today 0 - 18K -

  To display snapshot information by default, set the listsnapshots property. For example:

  # zpool get listsnapshots pool NAME PROPERTY VALUE SOURCE pool listsnapshots off default # zpool set listsnaps=on pool # zfs list NAME USED AVAIL REFER MOUNTPOINT pool 208K 6.71G 19K /pool pool/home 92K 6.71G 22K /pool/home pool/home@today 16K - 22K - pool/home/user1 18K 6.71G 18K /pool/home/user1 pool/home/user1@today 0 - 18K - pool/home/user2 18K 6.71G 18K /pool/home/user2 pool/home/user2@today 0 - 18K - pool/home/user3 18K 6.71G 18K /pool/home/user3 pool/home/user3@today 0 - 18K -

  Keep in mind that changing the default listsnapshots setting might cause the zfs list output to run slowly in a pool with many snapshots.