Storage: ZFS: Difference between revisions

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== Introduction ==
<!--PVE_IMPORT_START_MARKER-->
ZFS is a combined file system and logical volume manager designed by Sun Microsystems. Starting with Proxmox VE 3.4, the native Linux kernel port of the ZFS filesystem is introduced as optional file-system and also as an additional selection for the root file-system. There is no need for manually compiling ZFS, all packages are included (for both kernel branches, 2.6.32 and 3.10).
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{{#pvedocs:pve-storage-zfspool-plain.html}}
By using ZFS, its possible to achieve maximal enterprise features with low budget hardware but also high performance systems by leveraging SSD caching or even SSD only setups. ZFS can replace cost intense hardware raid cards by moderate CPU and memory load combined with easy management.
[[Category:Reference Documentation]]
<pvehide>
In the first release, there are two ways to use ZFS on Proxmox VE:
Storage pool type: zfspool
*as an local directory, supports all storage content types (instead of ext3 or ext4)
This backend allows you to access local ZFS pools (or ZFS file systems
*as zvol block-storage, currently supporting kvm images in raw format (new ZFS storage plugin)
inside such pools).
**The advantage of zvol is the snapshot capability on fs-level (fast)
Configuration
 
The backend supports the common storage properties content, nodes,
This articles describes how to use ZFS on Proxmox VE.
disable, and the following ZFS specific properties:
 
pool
=== General ZFS advantages ===
Select the ZFS pool/filesystem. All allocations are done within that
*Easy configuration and management with Proxmox VE GUI and CLI.
pool.
*Reliable
blocksize
*Protection against data corruption
Set ZFS blocksize parameter.
*Data compression on file-system level
sparse
*Snapshots
Use ZFS thin-provisioning. A sparse volume is a volume whose
*Copy-on-write clone
reservation is not equal to the volume size.
*Various raid levels: RAID0, RAID1, RAID10, RAIDZ-1, RAIDZ-2 and RAIDZ-3
mountpoint
*Can use SSD for cache
The mount point of the ZFS pool/filesystem. Changing this does not
*Self healing
affect the mountpoint property of the dataset seen by zfs.
*Continuous integrity checking
Defaults to /&lt;pool&gt;.
*Designed for high storage capacities
Configuration Example (/etc/pve/storage.cfg)
*Protection against data corruption
zfspool: vmdata
*Asynchrony replication over network
        pool tank/vmdata
*Open Source
        content rootdir,images
*Encryption
        sparse
*...
File naming conventions
 
The backend uses the following naming scheme for VM images:
== Hardware ==
vm-&lt;VMID&gt;-&lt;NAME&gt;      // normal VM images
ZFS depends heavily on memory, so you need at least 4GB to start. In practice, use as much you can get for your hardware/budget. To prevent data corruption, the use of high quality ECC RAM is very recommended.
base-&lt;VMID&gt;-&lt;NAME&gt;    // template VM image (read-only)
 
subvol-&lt;VMID&gt;-&lt;NAME&gt; // subvolumes (ZFS filesystem for containers)
If you use a dedicated cache and/or log disk, you should use a enterprise class SSD (e.g. Intel SSD DC S3700 Series). This can increase the overall performance quite significantly.
&lt;VMID&gt;
 
This specifies the owner VM.
If you are experimenting with an installation of Proxmox inside a VM ([[Nested_Virtualization]]), don't use Virtio for disks of that VM, since are not supported by ZFS, use IDE or SCSI (it's ok also with Virtio type contorller) instead.
&lt;NAME&gt;
 
This can be an arbitrary name (ascii) without white space. The
<b>IMPORTANT:</b> Do not use zfs on top of hardware controller which has it's own cache management. Zfs needs to directly communicate with disks, an HBA adapter is the way to go (or something like LSI controller flashed in 'IT' mode).
backend uses disk[N] as default, where [N] is replaced by an
 
integer to make the name unique.
== Installation as root file-system ==
Storage Features
[[Image:Screen-ISO-Install-ZFS.png|thumb]]
ZFS is probably the most advanced storage type regarding snapshot and
When you install with Proxmox-VE installer grater than 3.4. you can choose what FS you prefer.
cloning. The backend uses ZFS datasets for both VM images (format
 
raw) and container data (format subvol). ZFS properties are
It is not possible to use ZFS as rpool(root partition) with UEFI boot.
inherited from the parent dataset, so you can simply set defaults
 
on the parent dataset.
== Administration ==
Table 1. Storage features for backend zfs
=== Create a new ZPool ===
Content types
To create a zfspool, at least one disk is needed. The ashift should have the same sector-size (2 power of ashift) or larger as the underlying disk.
Image formats
zpool create -f -o ashift=12 <pool-name> <device>
Shared
To activate the compression
Snapshots
zfs set compression=lz4 <pool-name>
Clones
 
images rootdir
=== Create a new pool with RAID-0 ===
raw subvol
Minimum 1 Disk
no
zpool create -f -o ashift=12 <pool-name> <device1> <device2>
yes
=== Create a new pool with RAID-1 ===
yes
Minimum 2 Disks
Examples
zpool create -f -o ashift=12 <pool-name> mirror <device1> <device2>
It is recommended to create an extra ZFS file system to store your VM images:
=== Create a new pool with RAID-10 ===
# zfs create tank/vmdata
Minimum 4 Disks
To enable compression on that newly allocated file system:
zpool create -f -o ashift=12 <pool-name> mirror <device1> <device2> mirror <device3> <device4>
# zfs set compression=on tank/vmdata
=== Create a new pool with RAIDZ-1 ===
You can get a list of available ZFS filesystems with:
Minimum 3 Disks
# pvesm zfsscan
zpool create -f -o ashift=12 <pool-name> raidz1 <device1> <device2> <device3>
See Also
=== Create a new pool with RAIDZ-2 ===
Storage
Minimum 4 Disks
ZFS on Linux
zpool create -f -o ashift=12 <pool-name> raidz2 <device1> <device2> <device3> <device4>
</pvehide>
=== Create a new pool with Cache (L2ARC) ===
<!--PVE_IMPORT_END_MARKER-->
It is possible to use a dedicated cache drive partition to increase the performance (use SSD).
 
As <device> it is possible to use more devices, like it's shown in "Create a new pool with RAID*".
zpool create -f -o ashift=12 <pool-name> <device> cache <cache_device>
=== Create a new pool with Log (ZIL) ===
It is possible to use a dedicated cache drive partition to increase the performance(SSD).
 
As <device> it is possible to use more devices, like it's shown in "Create a new pool with RAID*".
zpool create -f -o ashift=12 <pool-name> <device> log <log_device>
=== Create a new pool with Cache and Log on one Disk ===
It is possible to create ZIL and L2ARC on one SSD. First partition the SSD in 2 partition with parted or gdisk (important: use GPT partition table).
 
As <device> it is possible to use more devices, like it's shown in "Create a new pool with RAID*".
'''Important: identify device with /dev/disk/by-id/scsi-*<device>''' 
zpool create -f -o ashift=12 <pool-name> <device> log <log_device>
Minimum 1 Disk
zpool create -f -o ashift=12 <pool-name> <device1> <device2>
=== Activate Email notification ===
ZFS >=0.64 has an Email notification daemon.
The daemon send an Email on zfs event like pool errors.
 
to activate the daemon it is necessary to edit /etc/zfs/zed.d/zed.rc with your favored editor.
 
<b>Important: the only settings what is required is ZED_EMAIL the other are optional.</b>
 
== Add Cache and Log to existing pool ==
If you have an pool without cache and log.
First partition the SSD in 2 partition with parted or gdisk (important: use GPT partition table).
 
'''Important: identify device with /dev/disk/by-id/scsi-*<device>''' 
zpool add -f <pool-name> cache <device1.part1> log <device1.part2>
 
'''Example: Proxmox with zfs as rootFS'''
zpool add -f rpool cache /dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_drive-scsi2-part1 \
log /dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_drive-scsi2-part2
 
== Changing a failed Device ==
zpool replace -f <pool-name> <old device> <new-device>
== Using ZFS Storage Plugin via Proxmox VE GUI ==
If the zpool is created, you can use it on Proxmox VE GUI and CLI.
=== Adding a ZFS storage via GUI ===
[[Image:Screen-Add-ZFS1.png|thumb]] [[Image:Screen-Add-ZFS2.png|thumb]]
Go to Datacenter/Storage and use the ZFSStorage plugin to add your zpool (select ZFS).
 
*ID is for identification of the Storage
*the checkbox ZFS Pool shows all existing pools (use CLI to create more)
*Thin provisioning: allocate not all space immediately by creating virtual disks
 
=== Adding a ZFS storage via CLI ===
To create it by CLI use
pvesm add zfspool <storage-ID> -pool <pool-name>
 
== Limit ZFS memory usage ==
It is good to use max 50 percent (which is default) of the system memory for ZFS arc to prevent performance shortage of the host.
 
Use your preferred editor to change the config in /etc/modprobe.d/zfs.conf and insert:
options zfs zfs_arc_max=4299967296
This example setting limits the usage to 4GB.
 
'''IMPORTANT: If your root fs is ZFS you must update your initramfs every time this value changes.'''
update-initramfs -u
 
If your Server has enough memory (i.e. you do not over commit memory) and you have a SWAP partition on ZFS lower the swappiness value to avoid problems and hang ups, a good value for servers is 10:
sysctl -w vm.swappiness=10
 
== Misc ==
=== QEMU tuning ===
see thread on proxmox forum, per user Nemesiz:
*pool:
zfs set primarycache=all tank
*kvm config:
* change cache to Write Back
:You can do it using web GUI or manually. Example:
ide0: data_zfs:100/vm-100-disk-1.raw,cache=writeback
if not set this happened:
<pre>
qm start 4016
kvm: -drive file=/data/pve-storage/images/4016/vm-4016-disk-1.raw,if=none,id=drive-virtio1,aio=native,cache=none: could not open disk image /data/pve-storage/images/4016/vm-4016-disk-1.raw: Invalid argument
</pre>
 
=== Example configurations for running Proxmox VE with ZFS ===
==== Install on a high performance system ====
As of 2013 and later, high performance servers have 16-64 cores, 256GB-1TB RAM and potentially many 2.5" disks and/or a PCIe based SSD with half a million IOPS. High performance systems benefit from a number of custom settings, for example enabling compression typically improves performance.
 
* If you have a good number of disks keep organized by using aliases. Edit /etc/zfs/vdev_id.conf to prepare aliases for disk devices found in /dev/disk/by-id/ :
# run 'udevadm trigger' after updating this file
alias a0        scsi-36848f690e856b10018cdf39854055206
alias b0        scsi-36848f690e856b10018cdf3ce573fdeb6
  alias a1        scsi-36848f690e856b10018cdf40f5b277cbc
alias b1        scsi-36848f690e856b10018cdf43a5db1b99b
alias a2        scsi-36848f690e856b10018cdf4575f652ad0
alias b2        scsi-36848f690e856b10018cdf47761587cec
 
Use flash for caching/logs. If you have only one SSD, use parted of gdisk to create a small partition for the ZIL (ZFS intent log) and a larger one for the L2ARC (ZFS read cache on disk). Make sure that the ZIL is on the first partition. In our case we have a Express Flash PCIe SSD with 175GB capacity and setup a ZIL with 25GB and a L2ARC cache partition of 150GB.
*edit /etc/modprobe.d/zfs.conf​ to apply several tuning options for high performance servers:
 
# ZFS tuning for a proxmox machine that reserves 64GB for ZFS
#
# Don't let ZFS use less than 4GB and more than 64GB
options zfs zfs_arc_min=4294967296
options zfs zfs_arc_max=68719476736
#
# disabling prefetch is no longer required
options zfs l2arc_noprefetch=0
 
*create a zpool of striped mirrors (equivalent to RAID10) with log device and cache and always enable compression:
 
zpool create -o compression=on -f tank mirror a0 b0 mirror a1 b1 mirror a2 b2 log /dev/rssda1 cache /dev/rssda2​
 
*​​​​​​​​check the status of the newly created pool:
 
<pre>
root@proxmox:/# zpool status
  pool: tank
state: ONLINE
  scan: none requested
config:
 
        NAME       STATE    READ WRITE CKSUM
        tank        ONLINE      0    0    0
          mirror-0  ONLINE      0    0    0
            a0      ONLINE      0    0    0
            b0      ONLINE      0    0    0
          mirror-1  ONLINE      0    0    0
            a1      ONLINE      0    0    0
            b1      ONLINE      0    0    0
          mirror-2  ONLINE      0    0    0
            a2      ONLINE      0    0    0
            b2      ONLINE      0    0    0
        logs
          rssda1    ONLINE      0    0    0
        cache
          rssda2    ONLINE      0    0    0
 
errors: No known data errors
</pre>
 
Using PVE 2.3 on a 2013 high performance system with ZFS you can install Windows Server 2012 Datacenter Edition with GUI in just under 4 minutes.
 
===How to prevent lvm of scanning zvols===
 
It is not necessary but to reduce confusion, when using lvm it is a good practice. 
 
open the config file /etc/lvm/lvm.conf
 
and insert the following line
 
filter = [ "r|/dev/zd*|" ]
 
== Troubleshooting and known issues ==
=== ZFS packages are not installed ===
If you upgraded to 3.4 or later, zfsutils package is not installed. You can install it with apt:
apt-get install zfsutils zfs-initramfs
 
=== Grub boot ZFS problem ===
*Symptoms: stuck at boot with an blinking prompt.
*Reason: If you ZFS raid it could happen that your mainboard does not initial all your disks correctly and Grub will wait for all RAID disk members - and fails. It can happen with more than 2 disks in ZFS RAID configuration - we saw this on some boards with ZFS RAID-0/RAID-10
=== ZFS mounting workaround ===
The default ZFS mount -a script runs too late in the boot process for most system scripts. The following helps to mount ZFS correctly. This is only necessary if you do not use ZFS as root file-system and if you use ZFS as an additional directory storage.
 
2014-01-22: the info below came from this excellent wiki page:  http://wiki.complete.org/ConvertingToZFS
 
*Edit /etc/default/zfs and set ZFS_MOUNT='yes'
 
*edit /etc/insserv.conf,
:and at the end of the $local_fs line,
:add zfs-mount (without a plus).
<pre>
#
# All local file-systems are mounted (done during boot phase)
#
$local_fs      +mountall +mountall-bootclean +mountoverflowtmp +umountfs
</pre>
 
edit /etc/init.d/zfs-mount and find three lines near the top, changing them like this:
<pre>
# Required-Start:
# Required-Stop:
# Default-Start: S
</pre>
''note remove the Required-Start and -Stop entries.''
 
*Activating init.d changes Then run:
<pre>
insserv -v -d zfs-mount
</pre>
 
I had an issue with pve storage on ZFS, before pve would start before ZFS and create directories at the ZFS mount point. To fix that start single user mode and remove the directories [ make sure  they are empty.... ].
 
also see https://github.com/zfsonlinux/pkg-zfs/issues/101
 
=== SWAP on ZFS ===
 
SWAP on ZFS on Linux may generate some Troubles, like blocking the server or generating a high IO load, often seen when starting a Backup to an external Storage.
To work around this follow [[#Limit ZFS memory usage]] and especially lower the vm.swappiness value.
 
=== Snapshot of LXC on ZFS ===
 
If you can't create a snapshot of an LXC container on ZFS and you get following message:
<pre>
INFO: rsync: set_acl: sys_acl_set_file(archiv, ACL_TYPE_DEFAULT): Operation not supported (95)
</pre>
 
you can run following commands 
<pre>
zfs create -o mountpoint=/mnt/vztmp rpool/vztmp
zfs set acltype=posixacl rpool/vztmp
</pre>
 
Now set /mnt/vztmp in your /etc/vzdump.conf for tmp
 
== Glossary ==
*ZPool is the logical unit of the underlying disks, what zfs use.
*ZVol is an emulated Block Device provided by ZFS
*ZIL is ZFS Intent Log
*ARC is Adaptive Replacement Cache and located in Ram
*L2ARC is Layer2 Adaptive Replacement Cache and should be on an fast device (like SSD).
 
== Further readings about ZFS ==
*http://wiki.illumos.org/download/attachments/1146951/zfs_last.pdf
*http://zfsonlinux.org/faq.html
*http://wiki.complete.org/ConvertingToZFS
*https://www.freebsd.org/doc/handbook/zfs.html (even if written for freebsd, of course, I found this doc is extremely clear even for less "techie" admins [note by m.ardito])
*https://pthree.org/2012/04/17/install-zfs-on-debian-gnulinux/ (and all other pages linked there)
 
and this has some very important information to know before implementing zfs on a production system.
*http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide
 
Very well written manual pages
man zfs
man zpool
 
[[Category:HOWTO]] [[Category:Installation]] [[Category:Technology]]

Latest revision as of 08:08, 6 December 2019

Storage pool type: zfspool

This backend allows you to access local ZFS pools (or ZFS file systems inside such pools).

Configuration

The backend supports the common storage properties content, nodes, disable, and the following ZFS specific properties:

pool

Select the ZFS pool/filesystem. All allocations are done within that pool.

blocksize

Set ZFS blocksize parameter.

sparse

Use ZFS thin-provisioning. A sparse volume is a volume whose reservation is not equal to the volume size.

mountpoint

The mount point of the ZFS pool/filesystem. Changing this does not affect the mountpoint property of the dataset seen by zfs. Defaults to /<pool>.

Configuration Example (/etc/pve/storage.cfg)
zfspool: vmdata
        pool tank/vmdata
        content rootdir,images
        sparse

File naming conventions

The backend uses the following naming scheme for VM images:

vm-<VMID>-<NAME>      // normal VM images
base-<VMID>-<NAME>    // template VM image (read-only)
subvol-<VMID>-<NAME>  // subvolumes (ZFS filesystem for containers)
<VMID>

This specifies the owner VM.

<NAME>

This can be an arbitrary name (ascii) without white space. The backend uses disk[N] as default, where [N] is replaced by an integer to make the name unique.

Storage Features

ZFS is probably the most advanced storage type regarding snapshot and cloning. The backend uses ZFS datasets for both VM images (format raw) and container data (format subvol). ZFS properties are inherited from the parent dataset, so you can simply set defaults on the parent dataset.

Table 1. Storage features for backend zfs
Content types Image formats Shared Snapshots Clones

images rootdir

raw subvol

no

yes

yes

Examples

It is recommended to create an extra ZFS file system to store your VM images:

# zfs create tank/vmdata

To enable compression on that newly allocated file system:

# zfs set compression=on tank/vmdata

You can get a list of available ZFS filesystems with:

# pvesm zfsscan

See Also


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