====== zfs cheatsheet ======

===== install zfs on centos 7.3 =====

([[https://github.com/zfsonlinux/zfs/wiki/RHEL-%26-CentOS#kabi-tracking-kmod|source]]):

1. install zfs repo:
  yum install http://download.zfsonlinux.org/epel/zfs-release.el7_3.noarch.rpm
2. disable zfs and enable zfs-kmod in /etc/yum.repos.d/zfs.repo

in order to automatically import pools on CentOS run this ([[https://github.com/zfsonlinux/zfs/wiki/RHEL-%26-CentOS#kabi-tracking-kmod|source]]):
  systemctl preset zfs-import-cache zfs-import-scan zfs-mount zfs-share zfs-zed zfs.target
  
===== Create pool =====

  zpool create -o mountpoint=/path/to/mount <name> <raid level> <dev1> <dev2> ...

Raid levels:
  - do not specify - none
  - **mirror** - RAID1
  - **raidz** or **raidz1** = RAID5
  - **raidz2** = RAID6
  - **raidz3** = "RAID7" or has 3 parity

example - create raid5 of 4 disks:
  zpool create -o mountpoint=/storage storage raidz /dev/sdb /dev/sdc /dev/sdd /dev/sde
  
===== Create Filesystems =====

Create filesystem

  zfs create [-o mountpoint=/path/to/mount] -o compression=lz4 <pool>/<fsname>
  
create sub-filesystem
  zfs create [-o mountpoint=/path/to/mount] -o compression=lz4 <pool>/<fsname>/<subfsname>

  
Default mount point is as a subdirectory of pool mount point. To set mount point:
  
  zfs set mountpoint=/path/to/mount <pool>/<fsname>
  
Remove filesystem

  zfs destroy [-f] <pool><filesystem>


===== cache =====

http://louwrentius.com/zfs-on-linux-monitor-cache-hit-ratio.html

===== MySQL =====

MySQL

This assumes lots of RAM

Tweaks for MySQL

  innodb_flush_log_at_trx_commit=2
  skip-innodb_doublewrite
Tweaks for ZFS

  zfs set primarycache=metadata tank/db
  zfs set atime=off tank/db
  zfs set recordsize=16k tank/db/innodb
  zfs set recordsize=128k tank/db/logs
  zfs set zfs:zfs_nocacheflush = 1
  zfs set sync=disabled tank/db
  
Note: MySQL 5.6.6 and newer (and related MariaDB / Percona forks) has innodb_file_per_table = on as default, so IBD files are not created under tank/db/innodb (defined by innodb_data_home_dir in your my.cnf), they are created under tank/db/<db_name>/ and you should use recordsize=16k on this dataset too or switch back to innodb_file_per_table = off


===== Links =====
  * [[https://wiki.freebsd.org/ZFSTuningGuide#L2ARC_discussion]] - optimization