* Copy-on-write clone
-* Various raid levels: RAID0, RAID1, RAID10, RAIDZ-1, RAIDZ-2 and RAIDZ-3
+* Various raid levels: RAID0, RAID1, RAID10, RAIDZ-1, RAIDZ-2, RAIDZ-3,
+dRAID, dRAID2, dRAID3
* Can use SSD for cache
* Designed for high storage capacities
-* Protection against data corruption
-
* Asynchronous replication over network
* Open Source
~~~~~~~~
ZFS depends heavily on memory, so you need at least 8GB to start. In
-practice, use as much you can get for your hardware/budget. To prevent
+practice, use as much as you can get for your hardware/budget. To prevent
data corruption, we recommend the use of high quality ECC RAM.
If you use a dedicated cache and/or log disk, you should use an
-enterprise class SSD (e.g. Intel SSD DC S3700 Series). This can
+enterprise class SSD. This can
increase the overall performance significantly.
-IMPORTANT: Do not use ZFS on top of hardware controller which has its
-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.
+IMPORTANT: Do not use ZFS on top of a hardware RAID controller which has its
+own cache management. ZFS needs to communicate directly with the disks. An
+HBA adapter or something like an LSI controller flashed in ``IT'' mode is more
+appropriate.
If you are experimenting with an installation of {pve} inside a VM
(Nested Virtualization), don't use `virtio` for disks of that VM,
-since they are not supported by ZFS. Use IDE or SCSI instead (works
-also with `virtio` SCSI controller type).
+as they are not supported by ZFS. Use IDE or SCSI instead (also works
+with the `virtio` SCSI controller type).
Installation as Root File System
errors: No known data errors
----
-The `zfs` command is used configure and manage your ZFS file
-systems. The following command lists all file systems after
-installation:
+The `zfs` command is used to configure and manage your ZFS file systems. The
+following command lists all file systems after installation:
----
# zfs list
There are a few factors to take into consideration when choosing the layout of
a ZFS pool. The basic building block of a ZFS pool is the virtual device, or
`vdev`. All vdevs in a pool are used equally and the data is striped among them
-(RAID0). Check the `zpool(8)` manpage for more details on vdevs.
+(RAID0). Check the `zpoolconcepts(7)` manpage for more details on vdevs.
[[sysadmin_zfs_raid_performance]]
Performance
parameters of interest are the IOPS (Input/Output Operations per Second) and
the bandwidth with which data can be written or read.
-A 'mirror' vdev (RAID1) will approximately behave like a single disk in regards
-to both parameters when writing data. When reading data if will behave like the
-number of disks in the mirror.
+A 'mirror' vdev (RAID1) will approximately behave like a single disk in regard
+to both parameters when writing data. When reading data the performance will
+scale linearly with the number of disks in the mirror.
A common situation is to have 4 disks. When setting it up as 2 mirror vdevs
(RAID10) the pool will have the write characteristics as two single disks in
-regard of IOPS and bandwidth. For read operations it will resemble 4 single
+regard to IOPS and bandwidth. For read operations it will resemble 4 single
disks.
A 'RAIDZ' of any redundancy level will approximately behave like a single disk
-in regard of IOPS with a lot of bandwidth. How much bandwidth depends on the
+in regard to IOPS with a lot of bandwidth. How much bandwidth depends on the
size of the RAIDZ vdev and the redundancy level.
+A 'dRAID' pool should match the performance of an equivalent 'RAIDZ' pool.
+
For running VMs, IOPS is the more important metric in most situations.
The `volblocksize` property can only be set when creating a ZVOL. The default
value can be changed in the storage configuration. When doing this, the guest
needs to be tuned accordingly and depending on the use case, the problem of
-write amplification if just moved from the ZFS layer up to the guest.
+write amplification is just moved from the ZFS layer up to the guest.
Using `ashift=9` when creating the pool can lead to bad
performance, depending on the disks underneath, and cannot be changed later on.
Mirror vdevs (RAID1, RAID10) have favorable behavior for VM workloads. Use
-them, unless your environmanet has specific needs and charactersitics where
+them, unless your environment has specific needs and characteristics where
RAIDZ performance characteristics are acceptable.
+ZFS dRAID
+~~~~~~~~~
+
+In a ZFS dRAID (declustered RAID) the hot spare drive(s) participate in the RAID.
+Their spare capacity is reserved and used for rebuilding when one drive fails.
+This provides, depending on the configuration, faster rebuilding compared to a
+RAIDZ in case of drive failure. More information can be found in the official
+OpenZFS documentation. footnote:[OpenZFS dRAID
+https://openzfs.github.io/openzfs-docs/Basic%20Concepts/dRAID%20Howto.html]
+
+NOTE: dRAID is intended for more than 10-15 disks in a dRAID. A RAIDZ
+setup should be better for a lower amount of disks in most use cases.
+
+NOTE: The GUI requires one more disk than the minimum (i.e. dRAID1 needs 3). It
+expects that a spare disk is added as well.
+
+ * `dRAID1` or `dRAID`: requires at least 2 disks, one can fail before data is
+lost
+ * `dRAID2`: requires at least 3 disks, two can fail before data is lost
+ * `dRAID3`: requires at least 4 disks, three can fail before data is lost
+
+
+Additional information can be found on the manual page:
+
+----
+# man zpoolconcepts
+----
+
+Spares and Data
+^^^^^^^^^^^^^^^
+The number of `spares` tells the system how many disks it should keep ready in
+case of a disk failure. The default value is 0 `spares`. Without spares,
+rebuilding won't get any speed benefits.
+
+`data` defines the number of devices in a redundancy group. The default value is
+8. Except when `disks - parity - spares` equal something less than 8, the lower
+number is used. In general, a smaller number of `data` devices leads to higher
+IOPS, better compression ratios and faster resilvering, but defining fewer data
+devices reduces the available storage capacity of the pool.
+
+
Bootloader
~~~~~~~~~~
-Depending on whether the system is booted in EFI or legacy BIOS mode the
-{pve} installer sets up either `grub` or `systemd-boot` as main bootloader.
-See the chapter on xref:sysboot[{pve} host bootladers] for details.
+{pve} uses xref:sysboot_proxmox_boot_tool[`proxmox-boot-tool`] to manage the
+bootloader configuration.
+See the chapter on xref:sysboot[{pve} host bootloaders] for details.
ZFS Administration
Create a new zpool
^^^^^^^^^^^^^^^^^^
-To create a new pool, at least one disk is needed. The `ashift` should
-have the same sector-size (2 power of `ashift`) or larger as the
-underlying disk.
+To create a new pool, at least one disk is needed. The `ashift` should have the
+same sector-size (2 power of `ashift`) or larger as the underlying disk.
----
# zpool create -f -o ashift=12 <pool> <device>
----
+[TIP]
+====
+Pool names must adhere to the following rules:
+
+* begin with a letter (a-z or A-Z)
+* contain only alphanumeric, `-`, `_`, `.`, `:` or ` ` (space) characters
+* must *not begin* with one of `mirror`, `raidz`, `draid` or `spare`
+* must not be `log`
+====
+
To activate compression (see section <<zfs_compression,Compression in ZFS>>):
----
# zpool create -f -o ashift=12 <pool> raidz2 <device1> <device2> <device3> <device4>
----
+Please read the section for
+xref:sysadmin_zfs_raid_considerations[ZFS RAID Level Considerations]
+to get a rough estimate on how IOPS and bandwidth expectations before setting up
+a pool, especially when wanting to use a RAID-Z mode.
+
[[sysadmin_zfs_create_new_zpool_with_cache]]
Create a new pool with cache (L2ARC)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-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*".
+It is possible to use a dedicated device, or partition, as second-level cache to
+increase the performance. Such a cache device will especially help with
+random-read workloads of data that is mostly static. As it acts as additional
+caching layer between the actual storage, and the in-memory ARC, it can also
+help if the ARC must be reduced due to memory constraints.
+.Create ZFS pool with a on-disk cache
----
-# zpool create -f -o ashift=12 <pool> <device> cache <cache_device>
+# zpool create -f -o ashift=12 <pool> <device> cache <cache-device>
----
+Here only a single `<device>` and a single `<cache-device>` was used, but it is
+possible to use more devices, like it's shown in
+xref:sysadmin_zfs_create_new_zpool_raid0[Create a new pool with RAID].
+
+Note that for cache devices no mirror or raid modi exist, they are all simply
+accumulated.
+
+If any cache device produces errors on read, ZFS will transparently divert that
+request to the underlying storage layer.
+
+
[[sysadmin_zfs_create_new_zpool_with_log]]
Create a new pool with log (ZIL)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-It is possible to use a dedicated cache drive partition to increase
-the performance(SSD).
+It is possible to use a dedicated drive, or partition, for the ZFS Intent Log
+(ZIL), it is mainly used to provide safe synchronous transactions, so often in
+performance critical paths like databases, or other programs that issue `fsync`
+operations more frequently.
+
+The pool is used as default ZIL location, diverting the ZIL IO load to a
+separate device can, help to reduce transaction latencies while relieving the
+main pool at the same time, increasing overall performance.
-As `<device>` it is possible to use more devices, like it's shown in
-"Create a new pool with RAID*".
+For disks to be used as log devices, directly or through a partition, it's
+recommend to:
+- use fast SSDs with power-loss protection, as those have much smaller commit
+ latencies.
+
+- Use at least a few GB for the partition (or whole device), but using more than
+ half of your installed memory won't provide you with any real advantage.
+
+.Create ZFS pool with separate log device
----
-# zpool create -f -o ashift=12 <pool> <device> log <log_device>
+# zpool create -f -o ashift=12 <pool> <device> log <log-device>
----
+In above example a single `<device>` and a single `<log-device>` is used, but you
+can also combine this with other RAID variants, as described in the
+xref:sysadmin_zfs_create_new_zpool_raid0[Create a new pool with RAID] section.
+
+You can also mirror the log device to multiple devices, this is mainly useful to
+ensure that performance doesn't immediately degrades if a single log device
+fails.
+
+If all log devices fail the ZFS main pool itself will be used again, until the
+log device(s) get replaced.
+
[[sysadmin_zfs_add_cache_and_log_dev]]
Add cache and log to an existing pool
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-If you have a pool without cache and log. First partition the SSD in
-2 partition with `parted` or `gdisk`
+If you have a pool without cache and log you can still add both, or just one of
+them, at any time.
-IMPORTANT: Always use GPT partition tables.
+For example, let's assume you got a good enterprise SSD with power-loss
+protection that you want to use for improving the overall performance of your
+pool.
-The maximum size of a log device should be about half the size of
-physical memory, so this is usually quite small. The rest of the SSD
-can be used as cache.
+As the maximum size of a log device should be about half the size of the
+installed physical memory, it means that the ZIL will mostly likely only take up
+a relatively small part of the SSD, the remaining space can be used as cache.
+First you have to create two GPT partitions on the SSD with `parted` or `gdisk`.
+
+Then you're ready to add them to an pool:
+
+.Add both, a separate log device and a second-level cache, to an existing pool
----
# zpool add -f <pool> log <device-part1> cache <device-part2>
----
+Just replay `<pool>`, `<device-part1>` and `<device-part2>` with the pool name
+and the two `/dev/disk/by-id/` paths to the partitions.
+
+You can also add ZIL and cache separately.
+
+.Add a log device to an existing ZFS pool
+----
+# zpool add <pool> log <log-device>
+----
+
+
[[sysadmin_zfs_change_failed_dev]]
Changing a failed device
^^^^^^^^^^^^^^^^^^^^^^^^
----
-# zpool replace -f <pool> <old device> <new device>
+# zpool replace -f <pool> <old-device> <new-device>
----
.Changing a failed bootable device
-Depending on how {pve} was installed it is either using `grub` or `systemd-boot`
-as bootloader (see xref:sysboot[Host Bootloader]).
+Depending on how {pve} was installed it is either using `systemd-boot` or GRUB
+through `proxmox-boot-tool` footnote:[Systems installed with {pve} 6.4 or later,
+EFI systems installed with {pve} 5.4 or later] or plain GRUB as bootloader (see
+xref:sysboot[Host Bootloader]). You can check by running:
+
+----
+# proxmox-boot-tool status
+----
The first steps of copying the partition table, reissuing GUIDs and replacing
the ZFS partition are the same. To make the system bootable from the new disk,
NOTE: Use the `zpool status -v` command to monitor how far the resilvering
process of the new disk has progressed.
-.With `systemd-boot`:
+.With `proxmox-boot-tool`:
----
-# pve-efiboot-tool format <new disk's ESP>
-# pve-efiboot-tool init <new disk's ESP>
+# proxmox-boot-tool format <new disk's ESP>
+# proxmox-boot-tool init <new disk's ESP> [grub]
----
NOTE: `ESP` stands for EFI System Partition, which is setup as partition #2 on
bootable disks setup by the {pve} installer since version 5.4. For details, see
-xref:sysboot_systemd_boot_setup[Setting up a new partition for use as synced ESP].
+xref:sysboot_proxmox_boot_setup[Setting up a new partition for use as synced ESP].
-.With `grub`:
+NOTE: Make sure to pass 'grub' as mode to `proxmox-boot-tool init` if
+`proxmox-boot-tool status` indicates your current disks are using GRUB,
+especially if Secure Boot is enabled!
+
+.With plain GRUB:
----
# grub-install <new disk>
----
+NOTE: Plain GRUB is only used on systems installed with {pve} 6.3 or earlier,
+which have not been manually migrated to using `proxmox-boot-tool` yet.
-Activate E-Mail Notification
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-ZFS comes with an event daemon, which monitors events generated by the
-ZFS kernel module. The daemon can also send emails on ZFS events like
-pool errors. Newer ZFS packages ship the daemon in a separate package,
-and you can install it using `apt-get`:
+Configure E-Mail Notification
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-----
-# apt-get install zfs-zed
-----
+ZFS comes with an event daemon `ZED`, which monitors events generated by the ZFS
+kernel module. The daemon can also send emails on ZFS events like pool errors.
+Newer ZFS packages ship the daemon in a separate `zfs-zed` package, which should
+already be installed by default in {pve}.
-To activate the daemon it is necessary to edit `/etc/zfs/zed.d/zed.rc` with your
-favourite editor, and uncomment the `ZED_EMAIL_ADDR` setting:
+You can configure the daemon via the file `/etc/zfs/zed.d/zed.rc` with your
+favorite editor. The required setting for email notification is
+`ZED_EMAIL_ADDR`, which is set to `root` by default.
--------
ZED_EMAIL_ADDR="root"
Please note {pve} forwards mails to `root` to the email address
configured for the root user.
-IMPORTANT: The only setting that is required is `ZED_EMAIL_ADDR`. All
-other settings are optional.
-
[[sysadmin_zfs_limit_memory_usage]]
Limit ZFS Memory Usage
~~~~~~~~~~~~~~~~~~~~~~
-It is good to use at most 50 percent (which is the default) of the
-system memory for ZFS ARC to prevent performance shortage of the
-host. Use your preferred editor to change the configuration in
-`/etc/modprobe.d/zfs.conf` and insert:
+ZFS uses '50 %' of the host memory for the **A**daptive **R**eplacement
+**C**ache (ARC) by default. For new installations starting with {pve} 8.1, the
+ARC usage limit will be set to '10 %' of the installed physical memory, clamped
+to a maximum of +16 GiB+. This value is written to `/etc/modprobe.d/zfs.conf`.
+
+Allocating enough memory for the ARC is crucial for IO performance, so reduce it
+with caution. As a general rule of thumb, allocate at least +2 GiB Base + 1
+GiB/TiB-Storage+. For example, if you have a pool with +8 TiB+ of available
+storage space then you should use +10 GiB+ of memory for the ARC.
+
+ZFS also enforces a minimum value of +64 MiB+.
+
+You can change the ARC usage limit for the current boot (a reboot resets this
+change again) by writing to the +zfs_arc_max+ module parameter directly:
+
+----
+ echo "$[10 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max
+----
+
+To *permanently change* the ARC limits, add (or change if already present) the
+following line to `/etc/modprobe.d/zfs.conf`:
--------
options zfs zfs_arc_max=8589934592
--------
-This example setting limits the usage to 8GB.
+This example setting limits the usage to 8 GiB ('8 * 2^30^').
+
+IMPORTANT: In case your desired +zfs_arc_max+ value is lower than or equal to
++zfs_arc_min+ (which defaults to 1/32 of the system memory), +zfs_arc_max+ will
+be ignored unless you also set +zfs_arc_min+ to at most +zfs_arc_max - 1+.
+
+----
+echo "$[8 * 1024*1024*1024 - 1]" >/sys/module/zfs/parameters/zfs_arc_min
+echo "$[8 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max
+----
+
+This example setting (temporarily) limits the usage to 8 GiB ('8 * 2^30^') on
+systems with more than 256 GiB of total memory, where simply setting
++zfs_arc_max+ alone would not work.
[IMPORTANT]
====
-If your root file system is ZFS you must update your initramfs every
+If your root file system is ZFS, you must update your initramfs every
time this value changes:
----
-# update-initramfs -u
+# update-initramfs -u -k all
----
+
+You *must reboot* to activate these changes.
====
We strongly recommend to use enough memory, so that you normally do not
run into low memory situations. Should you need or want to add swap, it is
-preferred to create a partition on a physical disk and use it as swapdevice.
+preferred to create a partition on a physical disk and use it as a swap device.
You can leave some space free for this purpose in the advanced options of the
installer. Additionally, you can lower the
``swappiness'' value. A good value for servers is 10:
Encrypted ZFS Datasets
~~~~~~~~~~~~~~~~~~~~~~
+WARNING: Native ZFS encryption in {pve} is experimental. Known limitations and
+issues include Replication with encrypted datasets
+footnote:[https://bugzilla.proxmox.com/show_bug.cgi?id=2350],
+as well as checksum errors when using Snapshots or ZVOLs.
+footnote:[https://github.com/openzfs/zfs/issues/11688]
+
ZFS on Linux version 0.8.0 introduced support for native encryption of
datasets. After an upgrade from previous ZFS on Linux versions, the encryption
feature can be enabled per pool:
----
WARNING: There is currently no support for booting from pools with encrypted
-datasets using Grub, and only limited support for automatically unlocking
+datasets using GRUB, and only limited support for automatically unlocking
encrypted datasets on boot. Older versions of ZFS without encryption support
will not be able to decrypt stored data.
ZFS datasets expose the `special_small_blocks=<size>` property. `size` can be
`0` to disable storing small file blocks on the `special` device or a power of
-two in the range between `512B` to `128K`. After setting the property new file
+two in the range between `512B` to `1M`. After setting the property new file
blocks smaller than `size` will be allocated on the `special` device.
IMPORTANT: If the value for `special_small_blocks` is greater than or equal to
----
# zfs set special_small_blocks=0 <pool>/<filesystem>
----
+
+[[sysadmin_zfs_features]]
+ZFS Pool Features
+~~~~~~~~~~~~~~~~~
+
+Changes to the on-disk format in ZFS are only made between major version changes
+and are specified through *features*. All features, as well as the general
+mechanism are well documented in the `zpool-features(5)` manpage.
+
+Since enabling new features can render a pool not importable by an older version
+of ZFS, this needs to be done actively by the administrator, by running
+`zpool upgrade` on the pool (see the `zpool-upgrade(8)` manpage).
+
+Unless you need to use one of the new features, there is no upside to enabling
+them.
+
+In fact, there are some downsides to enabling new features:
+
+* A system with root on ZFS, that still boots using GRUB will become
+ unbootable if a new feature is active on the rpool, due to the incompatible
+ implementation of ZFS in GRUB.
+* The system will not be able to import any upgraded pool when booted with an
+ older kernel, which still ships with the old ZFS modules.
+* Booting an older {pve} ISO to repair a non-booting system will likewise not
+ work.
+
+IMPORTANT: Do *not* upgrade your rpool if your system is still booted with
+GRUB, as this will render your system unbootable. This includes systems
+installed before {pve} 5.4, and systems booting with legacy BIOS boot (see
+xref:sysboot_determine_bootloader_used[how to determine the bootloader]).
+
+.Enable new features for a ZFS pool:
+----
+# zpool upgrade <pool>
+----
projects / pve-docs.git / blobdiff