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ZFS

Snapshots

Calculate snapshots size:

zfs get -Hp used | grep 2014 | awk -F' ' 'BEGIN { total=0 } { $total+=$3 } END { print $total/1024/1024; }'

Send-Recv backups

From local pool to local pool:

zfs send tank/public@snap1 | zfs recv backuptank/public

To remote pool over ssh:

zfs send tank/public@snap1 | ssh user@remotehost zfs recv tank/public

Incrementals to remote pool over ssh:

zfs send -i tank/public@snap1 tank/public@snap2 | ssh user@remotehost zfs recv tank/public
zfs send -i tank/public@snap2 tank/public@snap3 | ssh user@remotehost zfs recv tank/public
zfs send -i tank/public@snap3 tank/public@snap4 | ssh user@remotehost zfs recv tank/public

Errors

Dataset does not exist

Determine clone names:

zdb -d <poolname> | grep %

Destroy identified clones:

zfs destroy <clone-with-%-in-the-name>

Command may complain that dataset does not exist, and you should check again if there are more clones.

ACLs on Solaris

Check existing ACLs:

ls -v

Adding new ACLs (allow everything to group domain admins):

chmod -R  A+group:domain\ admins:read_data/write_data/execute:allow jakov.sosic
chmod -R  A+group:domain\ admins:list_directory/read_data/add_file/write_data/add_subdirectory/append_data/write_xattr/execute/write_attributes/write_acl/write_owner/delete/delete_child:allow

Get object number

Use zdb -O to determine the object number of the file:

zdb -O <pool>/<dataset> path/to/file

Dump detailed data for object:

zdb -ddddd <object_id>

Tunning

Basics

Check logical block size on vdevs:

smartctl -a /dev/sdX | grep -i block

If there is a NVME, command is:

nvme list

Depending on 512b vs 4k, create zpool with either ashift=9 or ashift=12:

zpool create -f -O compression=lz4 -O atime=off -o ashift=9 <pool_name> <list_of_vdevs>

Note: you can find out block vdev sector size like this.

Some settings (except for ashift) can be added later:

zfs set compression=lz4 xattr=sa atime=off tank
  • compression is good if we have modern CPU which is mostly idle
  • xattr=sa stores attributes to system attributes instead of storing them to a file in a hidden dir (more seeks while reading)

More info.

Resilver speed

Lower the number of ticks to delay prior to issuing a resilver I/O:

echo 0 > /sys/module/zfs/parameters/zfs_resilver_delay

Lower the idle time (number of clock ticks) by which the scan operation is delayed if the user I/O has been detected:

echo 0 > /sys/module/zfs/parameters/zfs_scan_idle

More info:

Resizing

Expand single vdev

Vdevs can be expanded only by replascing them. So in a virtual environment, one can do the following to expand zpool vdev:

zpool set autoexpand=on tank
zpool replace tank /dev/sdb /dev/sdc
wipefs -af /dev/sdb
zpool replace tank /dev/sdc /dev/sdb