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Added zfs notes to the knowledge base
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Michele Cereda
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knowledge base/zfs.md
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knowledge base/zfs.md
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# ZFS
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## TL;DR
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```shell
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# create a single device pool
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zpool create pool_name device
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# list pools
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zpool list
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# show pools configuration and status
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zpool status
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zpool status pool_name time_in_seconds
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# show pools i/o statistics
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zpool iostat
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zpool iostat pool_name -n 1
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# check a pool for errors
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# verifies the checksum of every block
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# very cpu and disk intensive
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zpool scrub pool_name
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# list all pools available for import
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zpool import
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# import a pool
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zpool import pool_name
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zpool import encrypted_pool_name -l
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# export a pool
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# unmounts all filesystems
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zpool export pool_name
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# show the history of all pool operations
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zpool history pool_name
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# create a mirrored pool
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zpool create pool_name mirror device1 device2 mirror device3 device4
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# add a cache (L2ARC) device to a pool
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zpool add pool_name cache cache_disk
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# show the current version of a pool
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zpool upgrade -v
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# upgrade pools
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zpool upgrade pool_name
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zpool upgrade -a
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# get a pool's properties
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zpool get all pool_name
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# add a vdev to a mirrored pool
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zpool attach pool_name first_drive_in_existing_mirror new_dev
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# destroy a pool
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zpool destroy pool_name
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# restore a destroyed pool
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# the pool needs to be reimported straight after the destroy command has been issued
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zpool import -D
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# get info about zpools features
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man zpool-features
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# list all available filesystems
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zfs list
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# mount or unmount filesystems
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# see 'zfs get mountpoint pool_name' for mountpoint's root path
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zfs mount -alv
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zfs unmount pool_name/filesystem_name
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# create a new filesystem
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zfs create pool_name/filesystem_name
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# delete a filesystem
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zfs destroy pool_name/filesystem_name
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# manage a snapshot
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zfs list -t snapshot # list all
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zfs list -r -t snapshot -o name,creation pool_name/filesystem_name # list recursively for a given volume, output only name and creation date
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zfs snapshot pool_name/filesystem_name@snapshot_name # create
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zfs destroy pool_name/filesystem_name@snapshot_name # destroy
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# query a file system or volume configuration (get properties)
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zfs get all pool_name
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zfs get all pool_name/filesystem_name
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# enable compression on a filesystem
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zfs set compression=on pool_name/filesystem_name
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# change mountpoint for a filesystem
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zfs set mountpoint=/my/mount/path pool_name/filesystem_name
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# get info about zfs volumes properties
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man zfs
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```
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## Gotchas
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- one **cannot shrink** a pool
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- one **cannot remove vdevs** after a pool is created
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- more than 9 drives in one RAIDZ can cause performance regression; use 2 RAIDZ with 5 drives each instead of 1 RAIDZ with 10 drives to avoid this
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- one can **add** hot spares to a RAIDZ1 or RAIDZ2 pool
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- one can replace a drive with a bigger one (but **not a smaller one**) one at a time
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- one can mix MIRROR, RAIDZ1 and RAIDZ2 in a pool
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- volumes need an **empty** folder to be mounted
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## Manjaro
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Manjaro has prebuilt modules for ZFS, which package is the kernel's package postfixed by `-zfs` (e.g. for `linux-515` it is `linux515-zfs`)
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```shell
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# install the modules' packages for all installed kernels
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sudo pamac install $(mhwd-kernel --listinstalled | grep '*' | awk -F '* ' '{print $2}' | xargs -I {} echo {}-zfs)
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```
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## Mac OS X
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Pool options (`-o option`):
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* `ashift=XX`
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* XX=9 for 512B sectors, XX=12 for 4KB sectors, XX=16 for 8KB sectors
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* [reference](http://open-zfs.org/wiki/Performance_tuning#Alignment_Shift_.28ashift.29)
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* `version=28`
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* compatibility with ZFS on Linux
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Filesystem options (`-O option`):
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* `atime=off`
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* `compression=on`
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* activates compression with the default algorithm
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* pool version 28 cannot use lz4
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* `copies=2`
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* number of copies of data stored for the dataset
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* `dedup=on`
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* deduplication
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* halves write speed
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* [reference](http://open-zfs.org/wiki/Performance_tuning#Deduplication)
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* `xattr=sa`
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```shell
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sudo zpool \
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create \
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-f \
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-o comment='LaCie Rugged USB-C 4T' \
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-o version=28 \
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-O casesensitivity=mixed \
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-O compression=on \
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-O com.apple.mimic_hfs=on \
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-O copies=2 \
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-O logbias=throughput \
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-O normalization=formD \
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-O xattr=sa \
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volume_name \
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disk2
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sudo zpool import -a
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```
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```sh
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sudo zpool \
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create \
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-f \
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-o ashift=12 \
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-o feature@allocation_classes=disabled \
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-o feature@async_destroy=enabled \
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-o feature@bookmarks=enabled \
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-o feature@device_removal=enabled \
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-o feature@embedded_data=enabled \
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-o feature@empty_bpobj=enabled \
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-o feature@enabled_txg=enabled \
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-o feature@encryption=disabled \
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-o feature@extensible_dataset=enabled \
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-o feature@hole_birth=enabled \
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-o feature@large_dnode=disabled \
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-o feature@obsolete_counts=enabled \
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-o feature@spacemap_histogram=enabled \
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-o feature@spacemap_v2=enabled \
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-o feature@zpool_checkpoint=enabled \
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-o feature@filesystem_limits=enabled \
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-o feature@multi_vdev_crash_dump=enabled \
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-o feature@lz4_compress=enabled \
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-o feature@project_quota=disabled \
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-o feature@resilver_defer=disabled \
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-o feature@sha512=enabled \
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-o feature@skein=enabled \
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-o feature@userobj_accounting=disabled \
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-O atime=off \
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-O relatime=on \
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-O compression=lz4 \
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-O logbias=throughput \
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-O normalization=formD \
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-O xattr=sa \
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volume_name \
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/dev/sdb
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```
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## Further readings
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- [ZFS support + kernel, best approach]
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- [cheat.sh/zfs]
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- [Oracle Solaris ZFS Administration Guide]
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- [How to Enable ZFS Deduplication]
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- [gentoo wiki]
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- [aaron toponce's article on zfs administration]
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- [archlinux wiki]
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- [article on zfs on linux]
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[aaron toponce's article on zfs administration]: https://pthree.org/2012/12/04/zfs-administration-part-i-vdevs/
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[archlinux wiki]: https://wiki.archlinux.org/index.php/ZFS
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[article on zfs on linux]: https://blog.heckel.io/2017/01/08/zfs-encryption-openzfs-zfs-on-linux
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[cheat.sh/zfs]: https://cheat.sh/zfs
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[gentoo wiki]: https://wiki.gentoo.org/wiki/ZFS
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[how to enable zfs deduplication]: https://linuxhint.com/zfs-deduplication/
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[oracle solaris zfs administration guide]: https://docs.oracle.com/cd/E19253-01/819-5461/index.html
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[zfs support + kernel, best approach]: https://forum.manjaro.org/t/zfs-support-kernel-best-approach/33329/2
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