8 ZFS is a combined file system and logical volume manager designed by
9 Sun Microsystems. Starting with {pve} 3.4, the native Linux
10 kernel port of the ZFS file system is introduced as optional
11 file system and also as an additional selection for the root
12 file system. There is no need for manually compile ZFS modules - all
13 packages are included.
15 By using ZFS, its possible to achieve maximum enterprise features with
16 low budget hardware, but also high performance systems by leveraging
17 SSD caching or even SSD only setups. ZFS can replace cost intense
18 hardware raid cards by moderate CPU and memory load combined with easy
21 .General ZFS advantages
23 * Easy configuration and management with {pve} GUI and CLI.
27 * Protection against data corruption
29 * Data compression on file system level
35 * Various raid levels: RAID0, RAID1, RAID10, RAIDZ-1, RAIDZ-2 and RAIDZ-3
37 * Can use SSD for cache
41 * Continuous integrity checking
43 * Designed for high storage capacities
45 * Asynchronous replication over network
57 ZFS depends heavily on memory, so you need at least 8GB to start. In
58 practice, use as much as you can get for your hardware/budget. To prevent
59 data corruption, we recommend the use of high quality ECC RAM.
61 If you use a dedicated cache and/or log disk, you should use an
62 enterprise class SSD (e.g. Intel SSD DC S3700 Series). This can
63 increase the overall performance significantly.
65 IMPORTANT: Do not use ZFS on top of a hardware RAID controller which has its
66 own cache management. ZFS needs to communicate directly with the disks. An
67 HBA adapter or something like an LSI controller flashed in ``IT'' mode is more
70 If you are experimenting with an installation of {pve} inside a VM
71 (Nested Virtualization), don't use `virtio` for disks of that VM,
72 as they are not supported by ZFS. Use IDE or SCSI instead (also works
73 with the `virtio` SCSI controller type).
76 Installation as Root File System
77 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
79 When you install using the {pve} installer, you can choose ZFS for the
80 root file system. You need to select the RAID type at installation
84 RAID0:: Also called ``striping''. The capacity of such volume is the sum
85 of the capacities of all disks. But RAID0 does not add any redundancy,
86 so the failure of a single drive makes the volume unusable.
88 RAID1:: Also called ``mirroring''. Data is written identically to all
89 disks. This mode requires at least 2 disks with the same size. The
90 resulting capacity is that of a single disk.
92 RAID10:: A combination of RAID0 and RAID1. Requires at least 4 disks.
94 RAIDZ-1:: A variation on RAID-5, single parity. Requires at least 3 disks.
96 RAIDZ-2:: A variation on RAID-5, double parity. Requires at least 4 disks.
98 RAIDZ-3:: A variation on RAID-5, triple parity. Requires at least 5 disks.
100 The installer automatically partitions the disks, creates a ZFS pool
101 called `rpool`, and installs the root file system on the ZFS subvolume
104 Another subvolume called `rpool/data` is created to store VM
105 images. In order to use that with the {pve} tools, the installer
106 creates the following configuration entry in `/etc/pve/storage.cfg`:
112 content images,rootdir
115 After installation, you can view your ZFS pool status using the
125 NAME STATE READ WRITE CKSUM
127 mirror-0 ONLINE 0 0 0
130 mirror-1 ONLINE 0 0 0
134 errors: No known data errors
137 The `zfs` command is used configure and manage your ZFS file
138 systems. The following command lists all file systems after
143 NAME USED AVAIL REFER MOUNTPOINT
144 rpool 4.94G 7.68T 96K /rpool
145 rpool/ROOT 702M 7.68T 96K /rpool/ROOT
146 rpool/ROOT/pve-1 702M 7.68T 702M /
147 rpool/data 96K 7.68T 96K /rpool/data
148 rpool/swap 4.25G 7.69T 64K -
152 [[sysadmin_zfs_raid_considerations]]
153 ZFS RAID Level Considerations
154 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
156 There are a few factors to take into consideration when choosing the layout of
157 a ZFS pool. The basic building block of a ZFS pool is the virtual device, or
158 `vdev`. All vdevs in a pool are used equally and the data is striped among them
159 (RAID0). Check the `zpool(8)` manpage for more details on vdevs.
161 [[sysadmin_zfs_raid_performance]]
165 Each `vdev` type has different performance behaviors. The two
166 parameters of interest are the IOPS (Input/Output Operations per Second) and
167 the bandwidth with which data can be written or read.
169 A 'mirror' vdev (RAID1) will approximately behave like a single disk in regards
170 to both parameters when writing data. When reading data if will behave like the
171 number of disks in the mirror.
173 A common situation is to have 4 disks. When setting it up as 2 mirror vdevs
174 (RAID10) the pool will have the write characteristics as two single disks in
175 regard of IOPS and bandwidth. For read operations it will resemble 4 single
178 A 'RAIDZ' of any redundancy level will approximately behave like a single disk
179 in regard of IOPS with a lot of bandwidth. How much bandwidth depends on the
180 size of the RAIDZ vdev and the redundancy level.
182 For running VMs, IOPS is the more important metric in most situations.
185 [[sysadmin_zfs_raid_size_space_usage_redundancy]]
186 Size, Space usage and Redundancy
187 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
189 While a pool made of 'mirror' vdevs will have the best performance
190 characteristics, the usable space will be 50% of the disks available. Less if a
191 mirror vdev consists of more than 2 disks, for example in a 3-way mirror. At
192 least one healthy disk per mirror is needed for the pool to stay functional.
194 The usable space of a 'RAIDZ' type vdev of N disks is roughly N-P, with P being
195 the RAIDZ-level. The RAIDZ-level indicates how many arbitrary disks can fail
196 without losing data. A special case is a 4 disk pool with RAIDZ2. In this
197 situation it is usually better to use 2 mirror vdevs for the better performance
198 as the usable space will be the same.
200 Another important factor when using any RAIDZ level is how ZVOL datasets, which
201 are used for VM disks, behave. For each data block the pool needs parity data
202 which is at least the size of the minimum block size defined by the `ashift`
203 value of the pool. With an ashift of 12 the block size of the pool is 4k. The
204 default block size for a ZVOL is 8k. Therefore, in a RAIDZ2 each 8k block
205 written will cause two additional 4k parity blocks to be written,
206 8k + 4k + 4k = 16k. This is of course a simplified approach and the real
207 situation will be slightly different with metadata, compression and such not
208 being accounted for in this example.
210 This behavior can be observed when checking the following properties of the
214 * `refreservation` (if the pool is not thin provisioned)
215 * `used` (if the pool is thin provisioned and without snapshots present)
218 # zfs get volsize,refreservation,used <pool>/vm-<vmid>-disk-X
221 `volsize` is the size of the disk as it is presented to the VM, while
222 `refreservation` shows the reserved space on the pool which includes the
223 expected space needed for the parity data. If the pool is thin provisioned, the
224 `refreservation` will be set to 0. Another way to observe the behavior is to
225 compare the used disk space within the VM and the `used` property. Be aware
226 that snapshots will skew the value.
228 There are a few options to counter the increased use of space:
230 * Increase the `volblocksize` to improve the data to parity ratio
231 * Use 'mirror' vdevs instead of 'RAIDZ'
232 * Use `ashift=9` (block size of 512 bytes)
234 The `volblocksize` property can only be set when creating a ZVOL. The default
235 value can be changed in the storage configuration. When doing this, the guest
236 needs to be tuned accordingly and depending on the use case, the problem of
237 write amplification if just moved from the ZFS layer up to the guest.
239 Using `ashift=9` when creating the pool can lead to bad
240 performance, depending on the disks underneath, and cannot be changed later on.
242 Mirror vdevs (RAID1, RAID10) have favorable behavior for VM workloads. Use
243 them, unless your environment has specific needs and characteristics where
244 RAIDZ performance characteristics are acceptable.
250 {pve} uses xref:sysboot_proxmox_boot_tool[`proxmox-boot-tool`] to manage the
251 bootloader configuration.
252 See the chapter on xref:sysboot[{pve} host bootloaders] for details.
258 This section gives you some usage examples for common tasks. ZFS
259 itself is really powerful and provides many options. The main commands
260 to manage ZFS are `zfs` and `zpool`. Both commands come with great
261 manual pages, which can be read with:
268 [[sysadmin_zfs_create_new_zpool]]
272 To create a new pool, at least one disk is needed. The `ashift` should
273 have the same sector-size (2 power of `ashift`) or larger as the
277 # zpool create -f -o ashift=12 <pool> <device>
280 To activate compression (see section <<zfs_compression,Compression in ZFS>>):
283 # zfs set compression=lz4 <pool>
286 [[sysadmin_zfs_create_new_zpool_raid0]]
287 Create a new pool with RAID-0
288 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
293 # zpool create -f -o ashift=12 <pool> <device1> <device2>
296 [[sysadmin_zfs_create_new_zpool_raid1]]
297 Create a new pool with RAID-1
298 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
303 # zpool create -f -o ashift=12 <pool> mirror <device1> <device2>
306 [[sysadmin_zfs_create_new_zpool_raid10]]
307 Create a new pool with RAID-10
308 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
313 # zpool create -f -o ashift=12 <pool> mirror <device1> <device2> mirror <device3> <device4>
316 [[sysadmin_zfs_create_new_zpool_raidz1]]
317 Create a new pool with RAIDZ-1
318 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
323 # zpool create -f -o ashift=12 <pool> raidz1 <device1> <device2> <device3>
326 Create a new pool with RAIDZ-2
327 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
332 # zpool create -f -o ashift=12 <pool> raidz2 <device1> <device2> <device3> <device4>
335 [[sysadmin_zfs_create_new_zpool_with_cache]]
336 Create a new pool with cache (L2ARC)
337 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
339 It is possible to use a dedicated cache drive partition to increase
340 the performance (use SSD).
342 As `<device>` it is possible to use more devices, like it's shown in
343 "Create a new pool with RAID*".
346 # zpool create -f -o ashift=12 <pool> <device> cache <cache_device>
349 [[sysadmin_zfs_create_new_zpool_with_log]]
350 Create a new pool with log (ZIL)
351 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
353 It is possible to use a dedicated cache drive partition to increase
354 the performance(SSD).
356 As `<device>` it is possible to use more devices, like it's shown in
357 "Create a new pool with RAID*".
360 # zpool create -f -o ashift=12 <pool> <device> log <log_device>
363 [[sysadmin_zfs_add_cache_and_log_dev]]
364 Add cache and log to an existing pool
365 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
367 If you have a pool without cache and log. First partition the SSD in
368 2 partition with `parted` or `gdisk`
370 IMPORTANT: Always use GPT partition tables.
372 The maximum size of a log device should be about half the size of
373 physical memory, so this is usually quite small. The rest of the SSD
374 can be used as cache.
377 # zpool add -f <pool> log <device-part1> cache <device-part2>
380 [[sysadmin_zfs_change_failed_dev]]
381 Changing a failed device
382 ^^^^^^^^^^^^^^^^^^^^^^^^
385 # zpool replace -f <pool> <old device> <new device>
388 .Changing a failed bootable device
390 Depending on how {pve} was installed it is either using `systemd-boot` or `grub`
391 through `proxmox-boot-tool`
392 footnote:[Systems installed with {pve} 6.4 or later, EFI systems installed with
393 {pve} 5.4 or later] or plain `grub` as bootloader (see
394 xref:sysboot[Host Bootloader]). You can check by running:
397 # proxmox-boot-tool status
400 The first steps of copying the partition table, reissuing GUIDs and replacing
401 the ZFS partition are the same. To make the system bootable from the new disk,
402 different steps are needed which depend on the bootloader in use.
405 # sgdisk <healthy bootable device> -R <new device>
406 # sgdisk -G <new device>
407 # zpool replace -f <pool> <old zfs partition> <new zfs partition>
410 NOTE: Use the `zpool status -v` command to monitor how far the resilvering
411 process of the new disk has progressed.
413 .With `proxmox-boot-tool`:
416 # proxmox-boot-tool format <new disk's ESP>
417 # proxmox-boot-tool init <new disk's ESP>
420 NOTE: `ESP` stands for EFI System Partition, which is setup as partition #2 on
421 bootable disks setup by the {pve} installer since version 5.4. For details, see
422 xref:sysboot_proxmox_boot_setup[Setting up a new partition for use as synced ESP].
427 # grub-install <new disk>
429 NOTE: plain `grub` is only used on systems installed with {pve} 6.3 or earlier,
430 which have not been manually migrated to using `proxmox-boot-tool` yet.
433 Configure E-Mail Notification
434 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
436 ZFS comes with an event daemon `ZED`, which monitors events generated by the ZFS
437 kernel module. The daemon can also send emails on ZFS events like pool errors.
438 Newer ZFS packages ship the daemon in a separate `zfs-zed` package, which should
439 already be installed by default in {pve}.
441 You can configure the daemon via the file `/etc/zfs/zed.d/zed.rc` with your
442 favorite editor. The required setting for email notification is
443 `ZED_EMAIL_ADDR`, which is set to `root` by default.
446 ZED_EMAIL_ADDR="root"
449 Please note {pve} forwards mails to `root` to the email address
450 configured for the root user.
453 [[sysadmin_zfs_limit_memory_usage]]
454 Limit ZFS Memory Usage
455 ~~~~~~~~~~~~~~~~~~~~~~
457 ZFS uses '50 %' of the host memory for the **A**daptive **R**eplacement
458 **C**ache (ARC) by default. Allocating enough memory for the ARC is crucial for
459 IO performance, so reduce it with caution. As a general rule of thumb, allocate
460 at least +2 GiB Base + 1 GiB/TiB-Storage+. For example, if you have a pool with
461 +8 TiB+ of available storage space then you should use +10 GiB+ of memory for
464 You can change the ARC usage limit for the current boot (a reboot resets this
465 change again) by writing to the +zfs_arc_max+ module parameter directly:
468 echo "$[10 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max
471 To *permanently change* the ARC limits, add the following line to
472 `/etc/modprobe.d/zfs.conf`:
475 options zfs zfs_arc_max=8589934592
478 This example setting limits the usage to 8 GiB ('8 * 2^30^').
480 IMPORTANT: In case your desired +zfs_arc_max+ value is lower than or equal to
481 +zfs_arc_min+ (which defaults to 1/32 of the system memory), +zfs_arc_max+ will
482 be ignored unless you also set +zfs_arc_min+ to at most +zfs_arc_max - 1+.
485 echo "$[8 * 1024*1024*1024 - 1]" >/sys/module/zfs/parameters/zfs_arc_min
486 echo "$[8 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max
489 This example setting (temporarily) limits the usage to 8 GiB ('8 * 2^30^') on
490 systems with more than 256 GiB of total memory, where simply setting
491 +zfs_arc_max+ alone would not work.
495 If your root file system is ZFS, you must update your initramfs every
496 time this value changes:
499 # update-initramfs -u -k all
502 You *must reboot* to activate these changes.
510 Swap-space created on a zvol may generate some troubles, like blocking the
511 server or generating a high IO load, often seen when starting a Backup
512 to an external Storage.
514 We strongly recommend to use enough memory, so that you normally do not
515 run into low memory situations. Should you need or want to add swap, it is
516 preferred to create a partition on a physical disk and use it as a swap device.
517 You can leave some space free for this purpose in the advanced options of the
518 installer. Additionally, you can lower the
519 ``swappiness'' value. A good value for servers is 10:
522 # sysctl -w vm.swappiness=10
525 To make the swappiness persistent, open `/etc/sysctl.conf` with
526 an editor of your choice and add the following line:
532 .Linux kernel `swappiness` parameter values
533 [width="100%",cols="<m,2d",options="header"]
534 |===========================================================
536 | vm.swappiness = 0 | The kernel will swap only to avoid
537 an 'out of memory' condition
538 | vm.swappiness = 1 | Minimum amount of swapping without
539 disabling it entirely.
540 | vm.swappiness = 10 | This value is sometimes recommended to
541 improve performance when sufficient memory exists in a system.
542 | vm.swappiness = 60 | The default value.
543 | vm.swappiness = 100 | The kernel will swap aggressively.
544 |===========================================================
547 Encrypted ZFS Datasets
548 ~~~~~~~~~~~~~~~~~~~~~~
550 WARNING: Native ZFS encryption in {pve} is experimental. Known limitations and
551 issues include Replication with encrypted datasets
552 footnote:[https://bugzilla.proxmox.com/show_bug.cgi?id=2350],
553 as well as checksum errors when using Snapshots or ZVOLs.
554 footnote:[https://github.com/openzfs/zfs/issues/11688]
556 ZFS on Linux version 0.8.0 introduced support for native encryption of
557 datasets. After an upgrade from previous ZFS on Linux versions, the encryption
558 feature can be enabled per pool:
561 # zpool get feature@encryption tank
562 NAME PROPERTY VALUE SOURCE
563 tank feature@encryption disabled local
565 # zpool set feature@encryption=enabled
567 # zpool get feature@encryption tank
568 NAME PROPERTY VALUE SOURCE
569 tank feature@encryption enabled local
572 WARNING: There is currently no support for booting from pools with encrypted
573 datasets using Grub, and only limited support for automatically unlocking
574 encrypted datasets on boot. Older versions of ZFS without encryption support
575 will not be able to decrypt stored data.
577 NOTE: It is recommended to either unlock storage datasets manually after
578 booting, or to write a custom unit to pass the key material needed for
579 unlocking on boot to `zfs load-key`.
581 WARNING: Establish and test a backup procedure before enabling encryption of
582 production data. If the associated key material/passphrase/keyfile has been
583 lost, accessing the encrypted data is no longer possible.
585 Encryption needs to be setup when creating datasets/zvols, and is inherited by
586 default to child datasets. For example, to create an encrypted dataset
587 `tank/encrypted_data` and configure it as storage in {pve}, run the following
591 # zfs create -o encryption=on -o keyformat=passphrase tank/encrypted_data
595 # pvesm add zfspool encrypted_zfs -pool tank/encrypted_data
598 All guest volumes/disks create on this storage will be encrypted with the
599 shared key material of the parent dataset.
601 To actually use the storage, the associated key material needs to be loaded
602 and the dataset needs to be mounted. This can be done in one step with:
605 # zfs mount -l tank/encrypted_data
606 Enter passphrase for 'tank/encrypted_data':
609 It is also possible to use a (random) keyfile instead of prompting for a
610 passphrase by setting the `keylocation` and `keyformat` properties, either at
611 creation time or with `zfs change-key` on existing datasets:
614 # dd if=/dev/urandom of=/path/to/keyfile bs=32 count=1
616 # zfs change-key -o keyformat=raw -o keylocation=file:///path/to/keyfile tank/encrypted_data
619 WARNING: When using a keyfile, special care needs to be taken to secure the
620 keyfile against unauthorized access or accidental loss. Without the keyfile, it
621 is not possible to access the plaintext data!
623 A guest volume created underneath an encrypted dataset will have its
624 `encryptionroot` property set accordingly. The key material only needs to be
625 loaded once per encryptionroot to be available to all encrypted datasets
628 See the `encryptionroot`, `encryption`, `keylocation`, `keyformat` and
629 `keystatus` properties, the `zfs load-key`, `zfs unload-key` and `zfs
630 change-key` commands and the `Encryption` section from `man zfs` for more
631 details and advanced usage.
638 When compression is enabled on a dataset, ZFS tries to compress all *new*
639 blocks before writing them and decompresses them on reading. Already
640 existing data will not be compressed retroactively.
642 You can enable compression with:
645 # zfs set compression=<algorithm> <dataset>
648 We recommend using the `lz4` algorithm, because it adds very little CPU
649 overhead. Other algorithms like `lzjb` and `gzip-N`, where `N` is an
650 integer from `1` (fastest) to `9` (best compression ratio), are also
651 available. Depending on the algorithm and how compressible the data is,
652 having compression enabled can even increase I/O performance.
654 You can disable compression at any time with:
657 # zfs set compression=off <dataset>
660 Again, only new blocks will be affected by this change.
663 [[sysadmin_zfs_special_device]]
667 Since version 0.8.0 ZFS supports `special` devices. A `special` device in a
668 pool is used to store metadata, deduplication tables, and optionally small
671 A `special` device can improve the speed of a pool consisting of slow spinning
672 hard disks with a lot of metadata changes. For example workloads that involve
673 creating, updating or deleting a large number of files will benefit from the
674 presence of a `special` device. ZFS datasets can also be configured to store
675 whole small files on the `special` device which can further improve the
676 performance. Use fast SSDs for the `special` device.
678 IMPORTANT: The redundancy of the `special` device should match the one of the
679 pool, since the `special` device is a point of failure for the whole pool.
681 WARNING: Adding a `special` device to a pool cannot be undone!
683 .Create a pool with `special` device and RAID-1:
686 # zpool create -f -o ashift=12 <pool> mirror <device1> <device2> special mirror <device3> <device4>
689 .Add a `special` device to an existing pool with RAID-1:
692 # zpool add <pool> special mirror <device1> <device2>
695 ZFS datasets expose the `special_small_blocks=<size>` property. `size` can be
696 `0` to disable storing small file blocks on the `special` device or a power of
697 two in the range between `512B` to `1M`. After setting the property new file
698 blocks smaller than `size` will be allocated on the `special` device.
700 IMPORTANT: If the value for `special_small_blocks` is greater than or equal to
701 the `recordsize` (default `128K`) of the dataset, *all* data will be written to
702 the `special` device, so be careful!
704 Setting the `special_small_blocks` property on a pool will change the default
705 value of that property for all child ZFS datasets (for example all containers
706 in the pool will opt in for small file blocks).
708 .Opt in for all file smaller than 4K-blocks pool-wide:
711 # zfs set special_small_blocks=4K <pool>
714 .Opt in for small file blocks for a single dataset:
717 # zfs set special_small_blocks=4K <pool>/<filesystem>
720 .Opt out from small file blocks for a single dataset:
723 # zfs set special_small_blocks=0 <pool>/<filesystem>
726 [[sysadmin_zfs_features]]
730 Changes to the on-disk format in ZFS are only made between major version changes
731 and are specified through *features*. All features, as well as the general
732 mechanism are well documented in the `zpool-features(5)` manpage.
734 Since enabling new features can render a pool not importable by an older version
735 of ZFS, this needs to be done actively by the administrator, by running
736 `zpool upgrade` on the pool (see the `zpool-upgrade(8)` manpage).
738 Unless you need to use one of the new features, there is no upside to enabling
741 In fact, there are some downsides to enabling new features:
743 * A system with root on ZFS, that still boots using `grub` will become
744 unbootable if a new feature is active on the rpool, due to the incompatible
745 implementation of ZFS in grub.
746 * The system will not be able to import any upgraded pool when booted with an
747 older kernel, which still ships with the old ZFS modules.
748 * Booting an older {pve} ISO to repair a non-booting system will likewise not
751 IMPORTANT: Do *not* upgrade your rpool if your system is still booted with
752 `grub`, as this will render your system unbootable. This includes systems
753 installed before {pve} 5.4, and systems booting with legacy BIOS boot (see
754 xref:sysboot_determine_bootloader_used[how to determine the bootloader]).
756 .Enable new features for a ZFS pool:
758 # zpool upgrade <pool>