401 lines
12 KiB
ReStructuredText
401 lines
12 KiB
ReStructuredText
ZFS on Linux
|
|
------------
|
|
|
|
ZFS is a combined file system and logical volume manager designed by
|
|
Sun Microsystems. There is no need to manually compile ZFS modules - all
|
|
packages are included.
|
|
|
|
By using ZFS, it's possible to achieve maximum 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.
|
|
|
|
General ZFS advantages
|
|
|
|
* Easy configuration and management with GUI and CLI.
|
|
* Reliable
|
|
* Protection against data corruption
|
|
* Data compression on file system level
|
|
* Snapshots
|
|
* Copy-on-write clone
|
|
* Various raid levels: RAID0, RAID1, RAID10, RAIDZ-1, RAIDZ-2 and RAIDZ-3
|
|
* Can use SSD for cache
|
|
* Self healing
|
|
* Continuous integrity checking
|
|
* Designed for high storage capacities
|
|
* Asynchronous replication over network
|
|
* Open Source
|
|
* Encryption
|
|
|
|
Hardware
|
|
~~~~~~~~~
|
|
|
|
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
|
|
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
|
|
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.
|
|
|
|
|
|
ZFS Administration
|
|
~~~~~~~~~~~~~~~~~~
|
|
|
|
This section gives you some usage examples for common tasks. ZFS
|
|
itself is really powerful and provides many options. The main commands
|
|
to manage ZFS are `zfs` and `zpool`. Both commands come with great
|
|
manual pages, which can be read with:
|
|
|
|
.. code-block:: console
|
|
|
|
# man zpool
|
|
# man zfs
|
|
|
|
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.
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool create -f -o ashift=12 <pool> <device>
|
|
|
|
Create a new pool with RAID-0
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Minimum 1 disk
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool create -f -o ashift=12 <pool> <device1> <device2>
|
|
|
|
Create a new pool with RAID-1
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Minimum 2 disks
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool create -f -o ashift=12 <pool> mirror <device1> <device2>
|
|
|
|
Create a new pool with RAID-10
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Minimum 4 disks
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool create -f -o ashift=12 <pool> mirror <device1> <device2> mirror <device3> <device4>
|
|
|
|
Create a new pool with RAIDZ-1
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Minimum 3 disks
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool create -f -o ashift=12 <pool> raidz1 <device1> <device2> <device3>
|
|
|
|
Create a new pool with RAIDZ-2
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Minimum 4 disks
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool create -f -o ashift=12 <pool> raidz2 <device1> <device2> <device3> <device4>
|
|
|
|
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*".
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool create -f -o ashift=12 <pool> <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*".
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool create -f -o ashift=12 <pool> <device> log <log_device>
|
|
|
|
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`
|
|
|
|
.. important:: Always use GPT partition tables.
|
|
|
|
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.
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool add -f <pool> log <device-part1> cache <device-part2>
|
|
|
|
|
|
Changing a failed device
|
|
^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool replace -f <pool> <old device> <new device>
|
|
|
|
|
|
Changing a failed bootable device
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
Depending on how Proxmox Backup was installed it is either using `grub` or `systemd-boot`
|
|
as bootloader.
|
|
|
|
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,
|
|
different steps are needed which depend on the bootloader in use.
|
|
|
|
.. code-block:: console
|
|
|
|
# sgdisk <healthy bootable device> -R <new device>
|
|
# sgdisk -G <new device>
|
|
# zpool replace -f <pool> <old zfs partition> <new zfs partition>
|
|
|
|
.. NOTE:: Use the `zpool status -v` command to monitor how far the resilvering process of the new disk has progressed.
|
|
|
|
With `systemd-boot`:
|
|
|
|
.. code-block:: console
|
|
|
|
# pve-efiboot-tool format <new disk's ESP>
|
|
# pve-efiboot-tool init <new disk's ESP>
|
|
|
|
.. 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].
|
|
|
|
With `grub`:
|
|
|
|
Usually `grub.cfg` is located in `/boot/grub/grub.cfg`
|
|
|
|
.. code-block:: console
|
|
|
|
# grub-install <new disk>
|
|
# grub-mkconfig -o /path/to/grub.cfg
|
|
|
|
|
|
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`:
|
|
|
|
.. code-block:: console
|
|
|
|
# apt-get install zfs-zed
|
|
|
|
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:
|
|
|
|
.. code-block:: console
|
|
|
|
ZED_EMAIL_ADDR="root"
|
|
|
|
Please note Proxmox Backup 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.
|
|
|
|
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:
|
|
|
|
.. code-block:: console
|
|
|
|
options zfs zfs_arc_max=8589934592
|
|
|
|
This example setting limits the usage to 8GB.
|
|
|
|
.. IMPORTANT:: If your root file system is ZFS you must update your initramfs every time this value changes:
|
|
|
|
.. code-block:: console
|
|
|
|
# update-initramfs -u
|
|
|
|
|
|
SWAP on ZFS
|
|
^^^^^^^^^^^
|
|
|
|
Swap-space created on a zvol may generate some troubles, like blocking the
|
|
server or generating a high IO load, often seen when starting a Backup
|
|
to an external Storage.
|
|
|
|
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.
|
|
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:
|
|
|
|
.. code-block:: console
|
|
|
|
# sysctl -w vm.swappiness=10
|
|
|
|
To make the swappiness persistent, open `/etc/sysctl.conf` with
|
|
an editor of your choice and add the following line:
|
|
|
|
.. code-block:: console
|
|
|
|
vm.swappiness = 10
|
|
|
|
.. table:: Linux kernel `swappiness` parameter values
|
|
:widths:auto
|
|
|
|
==================== ===============================================================
|
|
Value Strategy
|
|
==================== ===============================================================
|
|
vm.swappiness = 0 The kernel will swap only to avoid an 'out of memory' condition
|
|
vm.swappiness = 1 Minimum amount of swapping without disabling it entirely.
|
|
vm.swappiness = 10 Sometimes recommended to improve performance when sufficient memory exists in a system.
|
|
vm.swappiness = 60 The default value.
|
|
vm.swappiness = 100 The kernel will swap aggressively.
|
|
==================== ===============================================================
|
|
|
|
ZFS Compression
|
|
^^^^^^^^^^^^^^^
|
|
|
|
To activate compression:
|
|
.. code-block:: console
|
|
|
|
# zpool set compression=lz4 <pool>
|
|
|
|
We recommend using the `lz4` algorithm, since it adds very little CPU overhead.
|
|
Other algorithms such as `lzjb` and `gzip-N` (where `N` is an integer `1-9` representing
|
|
the compression ratio, 1 is fastest and 9 is best compression) are also available.
|
|
Depending on the algorithm and how compressible the data is, having compression enabled can even increase
|
|
I/O performance.
|
|
|
|
You can disable compression at any time with:
|
|
.. code-block:: console
|
|
|
|
# zfs set compression=off <dataset>
|
|
|
|
Only new blocks will be affected by this change.
|
|
|
|
ZFS Special Device
|
|
^^^^^^^^^^^^^^^^^^
|
|
|
|
Since version 0.8.0 ZFS supports `special` devices. A `special` device in a
|
|
pool is used to store metadata, deduplication tables, and optionally small
|
|
file blocks.
|
|
|
|
A `special` device can improve the speed of a pool consisting of slow spinning
|
|
hard disks with a lot of metadata changes. For example workloads that involve
|
|
creating, updating or deleting a large number of files will benefit from the
|
|
presence of a `special` device. ZFS datasets can also be configured to store
|
|
whole small files on the `special` device which can further improve the
|
|
performance. Use fast SSDs for the `special` device.
|
|
|
|
.. IMPORTANT:: The redundancy of the `special` device should match the one of the
|
|
pool, since the `special` device is a point of failure for the whole pool.
|
|
|
|
.. WARNING:: Adding a `special` device to a pool cannot be undone!
|
|
|
|
Create a pool with `special` device and RAID-1:
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool create -f -o ashift=12 <pool> mirror <device1> <device2> special mirror <device3> <device4>
|
|
|
|
Adding a `special` device to an existing pool with RAID-1:
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool add <pool> special mirror <device1> <device2>
|
|
|
|
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
|
|
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
|
|
the `recordsize` (default `128K`) of the dataset, *all* data will be written to
|
|
the `special` device, so be careful!
|
|
|
|
Setting the `special_small_blocks` property on a pool will change the default
|
|
value of that property for all child ZFS datasets (for example all containers
|
|
in the pool will opt in for small file blocks).
|
|
|
|
Opt in for all file smaller than 4K-blocks pool-wide:
|
|
|
|
.. code-block:: console
|
|
|
|
# zfs set special_small_blocks=4K <pool>
|
|
|
|
Opt in for small file blocks for a single dataset:
|
|
|
|
.. code-block:: console
|
|
|
|
# zfs set special_small_blocks=4K <pool>/<filesystem>
|
|
|
|
Opt out from small file blocks for a single dataset:
|
|
|
|
.. code-block:: console
|
|
|
|
# zfs set special_small_blocks=0 <pool>/<filesystem>
|
|
|
|
Troubleshooting
|
|
^^^^^^^^^^^^^^^
|
|
|
|
Corrupted cachefile
|
|
|
|
In case of a corrupted ZFS cachefile, some volumes may not be mounted during
|
|
boot until mounted manually later.
|
|
|
|
For each pool, run:
|
|
|
|
.. code-block:: console
|
|
|
|
# zpool set cachefile=/etc/zfs/zpool.cache POOLNAME
|
|
|
|
and afterwards update the `initramfs` by running:
|
|
|
|
.. code-block:: console
|
|
|
|
# update-initramfs -u -k all
|
|
|
|
and finally reboot your node.
|
|
|
|
Sometimes the ZFS cachefile can get corrupted, and `zfs-import-cache.service`
|
|
doesn't import the pools that aren't present in the cachefile.
|
|
|
|
Another workaround to this problem is enabling the `zfs-import-scan.service`,
|
|
which searches and imports pools via device scanning (usually slower).
|