ZFS

Links

• http://open-zfs.org
• http://www.edplese.com/samba-with-zfs.html
• ZFS calculator
• ZFS clustering
• https://jrs-s.net/2015/02/03/will-zfs-and-non-ecc-ram-kill-your-data/ ZFS and ECC]
• ZFS troubleshooting/disk replacement
• Creating a ZFS HA Cluster using shared or shared-nothing storage
• ZFS 101
• Raidz expansion
• Basic guide to working with zfs

Documentation

• zfs manpage
• ZFS on Linux
• openzfs wiki
• https://wiki.gentoo.org/wiki/ZFS
• ZFS cheatsheet
• http://wiki.freebsd.org/ZFSQuickStartGuide
• Opensolaris ZFS intro
• raidz types reference

ARC/Caching

• Configuring ZFS Cache for High-Speed IO
• ZFS Arc various sizes
• Activity of the ZFS ARC

Tuning ZFS

• ZFS Performance and Tuning
• Using and tuning ARC

Commands

arc_summary

cat /proc/spl/kstat/zfs/arcstats

Terms and acronyms

vdev

Virtual Device. ZFS Virtual disks

L2ARC

Level 2 Adaptive Replacement Cache

SSD cache

DMU

Data Management Unit

MFU

Most Frequently Used

MRU

Most Recently Used

HOWTO

Create zfs filesystem

zfs create poolname/fsname

this also creates mountpoint

Add vdev to pool

zpool add mypool raidz1 sdg sdh sdi

Replace disk in zfs

Some links

• https://itectec.com/ubuntu/ubuntu-replacing-a-dead-disk-in-a-zpool/

Get information first:

Name of disk

zpool status

Find uid of disk to replace

take it offline

zpool offline poolname ata-WDC_WD20EFRX-68EUZN0_WD-WCC4M5RLZC6V

Get the disk guid:

zdb

guid: 15233236897831806877

Get list of disk by id:

ls -al /dev/disk/by-id

Save the id, shutdown, replace disk, boot:

Find the new disk:

ls -al /dev/disk/by-id

Run replace command. The id is the guid of the old disk, name is of the new disk

zpool replace tank /dev/disk/by-id/13450850036953119346 /dev/disk/by-id/ata-ST4000VN000-1H4168_Z302FQVZ

Showing information about ZFS pools and datasets

Show pools with sizes

zpool list 

or

zpool list -H -o name,size

Show reservations on datasets

zfs list -o name,reservations

Swap on zfs

https://askubuntu.com/questions/228149/zfs-partition-as-swap

vdevs

multiple vdevs

Multiple vdevs in a zpool get striped. What about balance?

invalid vdev specification

Probably means you need -f

Tuning arc settings

See Tuning ZFS modules parameters

zfs_arc_max

Linux defaults to giving 50% of RAM to arc, this is when:

cat /sys/module/zfs/parameters/zfs_arc_max
0
grep c_max /proc/spl/kstat/zfs/arcstats

To change this:

echo 5368709120 > /sys/module/zfs/parameters/zfs_arc_max

and add to /etc/modprobe.d/zfs.conf

zfs zfs_arc_max=5368709120

maybe you need

echo 3 > /proc/sys/vm/drop_caches

Tune zfs_arc_dnode_limit_percent

Assuming zfs_arc_dnode_limit = 0:

echo 20 > /sys/module/zfs/parameters/zfs_arc_dnode_limit_percent

In /etc/modprobe.d/zfs.conf:

options zfs zfs_arc_dnode_limit_percent=20

FAQ

show status and disks

zpool status

show drives/pools

zfs list
      

check raid level

zfs list -a

Estimate raidz speeds

raidz1: N/(N-1) * IOPS
raidz2: N/(N-2) * IOPS
raidz3: N/(N-3) * IOPS