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0235c741 | 1 | [[chapter_zfs]] |
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2 | ZFS on Linux |
3 | ------------ | |
5f09af76 DM |
4 | ifdef::wiki[] |
5 | :pve-toplevel: | |
6 | endif::wiki[] | |
7 | ||
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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 | |
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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 | |
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13 | packages are included. |
14 | ||
5eba0743 | 15 | By using ZFS, its possible to achieve maximum enterprise features with |
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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 | |
19 | management. | |
20 | ||
21 | .General ZFS advantages | |
22 | ||
23 | * Easy configuration and management with {pve} GUI and CLI. | |
24 | ||
25 | * Reliable | |
26 | ||
27 | * Protection against data corruption | |
28 | ||
5eba0743 | 29 | * Data compression on file system level |
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30 | |
31 | * Snapshots | |
32 | ||
33 | * Copy-on-write clone | |
34 | ||
447596fd SH |
35 | * Various raid levels: RAID0, RAID1, RAID10, RAIDZ-1, RAIDZ-2, RAIDZ-3, |
36 | dRAID, dRAID2, dRAID3 | |
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37 | |
38 | * Can use SSD for cache | |
39 | ||
40 | * Self healing | |
41 | ||
42 | * Continuous integrity checking | |
43 | ||
44 | * Designed for high storage capacities | |
45 | ||
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46 | * Asynchronous replication over network |
47 | ||
48 | * Open Source | |
49 | ||
50 | * Encryption | |
51 | ||
52 | * ... | |
53 | ||
54 | ||
55 | Hardware | |
56 | ~~~~~~~~ | |
57 | ||
58 | ZFS depends heavily on memory, so you need at least 8GB to start. In | |
60ed554f | 59 | practice, use as much as you can get for your hardware/budget. To prevent |
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60 | data corruption, we recommend the use of high quality ECC RAM. |
61 | ||
d48bdcf2 | 62 | If you use a dedicated cache and/or log disk, you should use an |
0d4a93dc | 63 | enterprise class SSD. This can |
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64 | increase the overall performance significantly. |
65 | ||
60ed554f DW |
66 | IMPORTANT: Do not use ZFS on top of a hardware RAID controller which has its |
67 | own cache management. ZFS needs to communicate directly with the disks. An | |
68 | HBA adapter or something like an LSI controller flashed in ``IT'' mode is more | |
69 | appropriate. | |
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70 | |
71 | If you are experimenting with an installation of {pve} inside a VM | |
8c1189b6 | 72 | (Nested Virtualization), don't use `virtio` for disks of that VM, |
60ed554f DW |
73 | as they are not supported by ZFS. Use IDE or SCSI instead (also works |
74 | with the `virtio` SCSI controller type). | |
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75 | |
76 | ||
5eba0743 | 77 | Installation as Root File System |
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78 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
79 | ||
80 | When you install using the {pve} installer, you can choose ZFS for the | |
81 | root file system. You need to select the RAID type at installation | |
82 | time: | |
83 | ||
84 | [horizontal] | |
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85 | RAID0:: Also called ``striping''. The capacity of such volume is the sum |
86 | of the capacities of all disks. But RAID0 does not add any redundancy, | |
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87 | so the failure of a single drive makes the volume unusable. |
88 | ||
8c1189b6 | 89 | RAID1:: Also called ``mirroring''. Data is written identically to all |
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90 | disks. This mode requires at least 2 disks with the same size. The |
91 | resulting capacity is that of a single disk. | |
92 | ||
93 | RAID10:: A combination of RAID0 and RAID1. Requires at least 4 disks. | |
94 | ||
95 | RAIDZ-1:: A variation on RAID-5, single parity. Requires at least 3 disks. | |
96 | ||
97 | RAIDZ-2:: A variation on RAID-5, double parity. Requires at least 4 disks. | |
98 | ||
99 | RAIDZ-3:: A variation on RAID-5, triple parity. Requires at least 5 disks. | |
100 | ||
101 | The installer automatically partitions the disks, creates a ZFS pool | |
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102 | called `rpool`, and installs the root file system on the ZFS subvolume |
103 | `rpool/ROOT/pve-1`. | |
9ee94323 | 104 | |
8c1189b6 | 105 | Another subvolume called `rpool/data` is created to store VM |
9ee94323 | 106 | images. In order to use that with the {pve} tools, the installer |
8c1189b6 | 107 | creates the following configuration entry in `/etc/pve/storage.cfg`: |
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108 | |
109 | ---- | |
110 | zfspool: local-zfs | |
111 | pool rpool/data | |
112 | sparse | |
113 | content images,rootdir | |
114 | ---- | |
115 | ||
116 | After installation, you can view your ZFS pool status using the | |
8c1189b6 | 117 | `zpool` command: |
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118 | |
119 | ---- | |
120 | # zpool status | |
121 | pool: rpool | |
122 | state: ONLINE | |
123 | scan: none requested | |
124 | config: | |
125 | ||
126 | NAME STATE READ WRITE CKSUM | |
127 | rpool ONLINE 0 0 0 | |
128 | mirror-0 ONLINE 0 0 0 | |
129 | sda2 ONLINE 0 0 0 | |
130 | sdb2 ONLINE 0 0 0 | |
131 | mirror-1 ONLINE 0 0 0 | |
132 | sdc ONLINE 0 0 0 | |
133 | sdd ONLINE 0 0 0 | |
134 | ||
135 | errors: No known data errors | |
136 | ---- | |
137 | ||
8c1189b6 | 138 | The `zfs` command is used configure and manage your ZFS file |
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139 | systems. The following command lists all file systems after |
140 | installation: | |
141 | ||
142 | ---- | |
143 | # zfs list | |
144 | NAME USED AVAIL REFER MOUNTPOINT | |
145 | rpool 4.94G 7.68T 96K /rpool | |
146 | rpool/ROOT 702M 7.68T 96K /rpool/ROOT | |
147 | rpool/ROOT/pve-1 702M 7.68T 702M / | |
148 | rpool/data 96K 7.68T 96K /rpool/data | |
149 | rpool/swap 4.25G 7.69T 64K - | |
150 | ---- | |
151 | ||
152 | ||
e4262cac AL |
153 | [[sysadmin_zfs_raid_considerations]] |
154 | ZFS RAID Level Considerations | |
155 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
156 | ||
157 | There are a few factors to take into consideration when choosing the layout of | |
158 | a ZFS pool. The basic building block of a ZFS pool is the virtual device, or | |
159 | `vdev`. All vdevs in a pool are used equally and the data is striped among them | |
160 | (RAID0). Check the `zpool(8)` manpage for more details on vdevs. | |
161 | ||
162 | [[sysadmin_zfs_raid_performance]] | |
163 | Performance | |
164 | ^^^^^^^^^^^ | |
165 | ||
166 | Each `vdev` type has different performance behaviors. The two | |
167 | parameters of interest are the IOPS (Input/Output Operations per Second) and | |
168 | the bandwidth with which data can be written or read. | |
169 | ||
f1b7d1a3 MH |
170 | A 'mirror' vdev (RAID1) will approximately behave like a single disk in regard |
171 | to both parameters when writing data. When reading data the performance will | |
172 | scale linearly with the number of disks in the mirror. | |
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173 | |
174 | A common situation is to have 4 disks. When setting it up as 2 mirror vdevs | |
175 | (RAID10) the pool will have the write characteristics as two single disks in | |
f1b7d1a3 | 176 | regard to IOPS and bandwidth. For read operations it will resemble 4 single |
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177 | disks. |
178 | ||
179 | A 'RAIDZ' of any redundancy level will approximately behave like a single disk | |
f1b7d1a3 | 180 | in regard to IOPS with a lot of bandwidth. How much bandwidth depends on the |
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181 | size of the RAIDZ vdev and the redundancy level. |
182 | ||
183 | For running VMs, IOPS is the more important metric in most situations. | |
184 | ||
185 | ||
186 | [[sysadmin_zfs_raid_size_space_usage_redundancy]] | |
187 | Size, Space usage and Redundancy | |
188 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
189 | ||
190 | While a pool made of 'mirror' vdevs will have the best performance | |
191 | characteristics, the usable space will be 50% of the disks available. Less if a | |
192 | mirror vdev consists of more than 2 disks, for example in a 3-way mirror. At | |
193 | least one healthy disk per mirror is needed for the pool to stay functional. | |
194 | ||
195 | The usable space of a 'RAIDZ' type vdev of N disks is roughly N-P, with P being | |
196 | the RAIDZ-level. The RAIDZ-level indicates how many arbitrary disks can fail | |
197 | without losing data. A special case is a 4 disk pool with RAIDZ2. In this | |
198 | situation it is usually better to use 2 mirror vdevs for the better performance | |
199 | as the usable space will be the same. | |
200 | ||
201 | Another important factor when using any RAIDZ level is how ZVOL datasets, which | |
202 | are used for VM disks, behave. For each data block the pool needs parity data | |
203 | which is at least the size of the minimum block size defined by the `ashift` | |
204 | value of the pool. With an ashift of 12 the block size of the pool is 4k. The | |
205 | default block size for a ZVOL is 8k. Therefore, in a RAIDZ2 each 8k block | |
206 | written will cause two additional 4k parity blocks to be written, | |
207 | 8k + 4k + 4k = 16k. This is of course a simplified approach and the real | |
208 | situation will be slightly different with metadata, compression and such not | |
209 | being accounted for in this example. | |
210 | ||
211 | This behavior can be observed when checking the following properties of the | |
212 | ZVOL: | |
213 | ||
214 | * `volsize` | |
215 | * `refreservation` (if the pool is not thin provisioned) | |
216 | * `used` (if the pool is thin provisioned and without snapshots present) | |
217 | ||
218 | ---- | |
219 | # zfs get volsize,refreservation,used <pool>/vm-<vmid>-disk-X | |
220 | ---- | |
221 | ||
222 | `volsize` is the size of the disk as it is presented to the VM, while | |
223 | `refreservation` shows the reserved space on the pool which includes the | |
224 | expected space needed for the parity data. If the pool is thin provisioned, the | |
225 | `refreservation` will be set to 0. Another way to observe the behavior is to | |
226 | compare the used disk space within the VM and the `used` property. Be aware | |
227 | that snapshots will skew the value. | |
228 | ||
229 | There are a few options to counter the increased use of space: | |
230 | ||
231 | * Increase the `volblocksize` to improve the data to parity ratio | |
232 | * Use 'mirror' vdevs instead of 'RAIDZ' | |
233 | * Use `ashift=9` (block size of 512 bytes) | |
234 | ||
235 | The `volblocksize` property can only be set when creating a ZVOL. The default | |
236 | value can be changed in the storage configuration. When doing this, the guest | |
237 | needs to be tuned accordingly and depending on the use case, the problem of | |
b2444770 | 238 | write amplification is just moved from the ZFS layer up to the guest. |
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239 | |
240 | Using `ashift=9` when creating the pool can lead to bad | |
241 | performance, depending on the disks underneath, and cannot be changed later on. | |
242 | ||
243 | Mirror vdevs (RAID1, RAID10) have favorable behavior for VM workloads. Use | |
f4abc68a | 244 | them, unless your environment has specific needs and characteristics where |
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245 | RAIDZ performance characteristics are acceptable. |
246 | ||
247 | ||
447596fd SH |
248 | ZFS dRAID |
249 | ~~~~~~~~~ | |
250 | ||
251 | In a ZFS dRAID (declustered RAID) the hot spare drive(s) participate in the RAID. | |
252 | Their spare capacity is reserved and used for rebuilding when one drive fails. | |
253 | This provides, depending on the configuration, faster rebuilding compared to a | |
254 | RAIDZ in case of drive failure. More information can be found in the official | |
255 | OpenZFS documentation. footnote:[OpenZFS dRAID | |
256 | https://openzfs.github.io/openzfs-docs/Basic%20Concepts/dRAID%20Howto.html] | |
257 | ||
258 | NOTE: dRAID is intended for more than 10-15 disks in a dRAID. A RAIDZ | |
259 | setup should be better for a lower amount of disks in most use cases. | |
260 | ||
261 | NOTE: The GUI requires one more disk than the minimum (i.e. dRAID1 needs 3). It | |
262 | expects that a spare disk is added as well. | |
263 | ||
264 | * `dRAID1` or `dRAID`: requires at least 2 disks, one can fail before data is | |
265 | lost | |
266 | * `dRAID2`: requires at least 3 disks, two can fail before data is lost | |
267 | * `dRAID3`: requires at least 4 disks, three can fail before data is lost | |
268 | ||
269 | ||
270 | Additional information can be found on the manual page: | |
271 | ||
272 | ---- | |
273 | # man zpoolconcepts | |
274 | ---- | |
275 | ||
276 | Spares and Data | |
277 | ^^^^^^^^^^^^^^^ | |
278 | The number of `spares` tells the system how many disks it should keep ready in | |
279 | case of a disk failure. The default value is 0 `spares`. Without spares, | |
280 | rebuilding won't get any speed benefits. | |
281 | ||
282 | `data` defines the number of devices in a redundancy group. The default value is | |
283 | 8. Except when `disks - parity - spares` equal something less than 8, the lower | |
284 | number is used. In general, a smaller number of `data` devices leads to higher | |
285 | IOPS, better compression ratios and faster resilvering, but defining fewer data | |
286 | devices reduces the available storage capacity of the pool. | |
287 | ||
288 | ||
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289 | Bootloader |
290 | ~~~~~~~~~~ | |
291 | ||
cb04e768 SI |
292 | {pve} uses xref:sysboot_proxmox_boot_tool[`proxmox-boot-tool`] to manage the |
293 | bootloader configuration. | |
3a433e9b | 294 | See the chapter on xref:sysboot[{pve} host bootloaders] for details. |
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295 | |
296 | ||
297 | ZFS Administration | |
298 | ~~~~~~~~~~~~~~~~~~ | |
299 | ||
300 | This section gives you some usage examples for common tasks. ZFS | |
301 | itself is really powerful and provides many options. The main commands | |
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302 | to manage ZFS are `zfs` and `zpool`. Both commands come with great |
303 | manual pages, which can be read with: | |
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304 | |
305 | ---- | |
306 | # man zpool | |
307 | # man zfs | |
308 | ----- | |
309 | ||
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310 | [[sysadmin_zfs_create_new_zpool]] |
311 | Create a new zpool | |
312 | ^^^^^^^^^^^^^^^^^^ | |
9ee94323 | 313 | |
25b89d16 TL |
314 | To create a new pool, at least one disk is needed. The `ashift` should have the |
315 | same sector-size (2 power of `ashift`) or larger as the underlying disk. | |
9ee94323 | 316 | |
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317 | ---- |
318 | # zpool create -f -o ashift=12 <pool> <device> | |
319 | ---- | |
9ee94323 | 320 | |
25b89d16 TL |
321 | [TIP] |
322 | ==== | |
323 | Pool names must adhere to the following rules: | |
324 | ||
325 | * begin with a letter (a-z or A-Z) | |
326 | * contain only alphanumeric, `-`, `_`, `.`, `:` or ` ` (space) characters | |
327 | * must *not begin* with one of `mirror`, `raidz`, `draid` or `spare` | |
328 | * must not be `log` | |
329 | ==== | |
330 | ||
e06707f2 | 331 | To activate compression (see section <<zfs_compression,Compression in ZFS>>): |
9ee94323 | 332 | |
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333 | ---- |
334 | # zfs set compression=lz4 <pool> | |
335 | ---- | |
9ee94323 | 336 | |
42449bdf TL |
337 | [[sysadmin_zfs_create_new_zpool_raid0]] |
338 | Create a new pool with RAID-0 | |
339 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
9ee94323 | 340 | |
dc2d00a0 | 341 | Minimum 1 disk |
9ee94323 | 342 | |
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343 | ---- |
344 | # zpool create -f -o ashift=12 <pool> <device1> <device2> | |
345 | ---- | |
9ee94323 | 346 | |
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347 | [[sysadmin_zfs_create_new_zpool_raid1]] |
348 | Create a new pool with RAID-1 | |
349 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
9ee94323 | 350 | |
dc2d00a0 | 351 | Minimum 2 disks |
9ee94323 | 352 | |
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353 | ---- |
354 | # zpool create -f -o ashift=12 <pool> mirror <device1> <device2> | |
355 | ---- | |
9ee94323 | 356 | |
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357 | [[sysadmin_zfs_create_new_zpool_raid10]] |
358 | Create a new pool with RAID-10 | |
359 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
9ee94323 | 360 | |
dc2d00a0 | 361 | Minimum 4 disks |
9ee94323 | 362 | |
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363 | ---- |
364 | # zpool create -f -o ashift=12 <pool> mirror <device1> <device2> mirror <device3> <device4> | |
365 | ---- | |
9ee94323 | 366 | |
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367 | [[sysadmin_zfs_create_new_zpool_raidz1]] |
368 | Create a new pool with RAIDZ-1 | |
369 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
9ee94323 | 370 | |
dc2d00a0 | 371 | Minimum 3 disks |
9ee94323 | 372 | |
eaefe614 FE |
373 | ---- |
374 | # zpool create -f -o ashift=12 <pool> raidz1 <device1> <device2> <device3> | |
375 | ---- | |
9ee94323 | 376 | |
42449bdf TL |
377 | Create a new pool with RAIDZ-2 |
378 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
9ee94323 | 379 | |
dc2d00a0 | 380 | Minimum 4 disks |
9ee94323 | 381 | |
eaefe614 FE |
382 | ---- |
383 | # zpool create -f -o ashift=12 <pool> raidz2 <device1> <device2> <device3> <device4> | |
384 | ---- | |
9ee94323 | 385 | |
42449bdf TL |
386 | [[sysadmin_zfs_create_new_zpool_with_cache]] |
387 | Create a new pool with cache (L2ARC) | |
388 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
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389 | |
390 | It is possible to use a dedicated cache drive partition to increase | |
391 | the performance (use SSD). | |
392 | ||
8c1189b6 | 393 | As `<device>` it is possible to use more devices, like it's shown in |
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394 | "Create a new pool with RAID*". |
395 | ||
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396 | ---- |
397 | # zpool create -f -o ashift=12 <pool> <device> cache <cache_device> | |
398 | ---- | |
9ee94323 | 399 | |
42449bdf TL |
400 | [[sysadmin_zfs_create_new_zpool_with_log]] |
401 | Create a new pool with log (ZIL) | |
402 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
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403 | |
404 | It is possible to use a dedicated cache drive partition to increase | |
405 | the performance(SSD). | |
406 | ||
8c1189b6 | 407 | As `<device>` it is possible to use more devices, like it's shown in |
9ee94323 DM |
408 | "Create a new pool with RAID*". |
409 | ||
eaefe614 FE |
410 | ---- |
411 | # zpool create -f -o ashift=12 <pool> <device> log <log_device> | |
412 | ---- | |
9ee94323 | 413 | |
42449bdf TL |
414 | [[sysadmin_zfs_add_cache_and_log_dev]] |
415 | Add cache and log to an existing pool | |
416 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
9ee94323 | 417 | |
b2444770 MH |
418 | If you have a pool without cache and log, first create 2 partitions on the SSD |
419 | with `parted` or `gdisk`. | |
9ee94323 | 420 | |
e300cf7d | 421 | IMPORTANT: Always use GPT partition tables. |
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422 | |
423 | The maximum size of a log device should be about half the size of | |
424 | physical memory, so this is usually quite small. The rest of the SSD | |
5eba0743 | 425 | can be used as cache. |
9ee94323 | 426 | |
eaefe614 | 427 | ---- |
237007eb | 428 | # zpool add -f <pool> log <device-part1> cache <device-part2> |
eaefe614 | 429 | ---- |
9ee94323 | 430 | |
42449bdf TL |
431 | [[sysadmin_zfs_change_failed_dev]] |
432 | Changing a failed device | |
433 | ^^^^^^^^^^^^^^^^^^^^^^^^ | |
9ee94323 | 434 | |
eaefe614 FE |
435 | ---- |
436 | # zpool replace -f <pool> <old device> <new device> | |
437 | ---- | |
1748211a | 438 | |
11a6e022 AL |
439 | .Changing a failed bootable device |
440 | ||
69c2b2e5 SI |
441 | Depending on how {pve} was installed it is either using `systemd-boot` or `grub` |
442 | through `proxmox-boot-tool` | |
cb04e768 SI |
443 | footnote:[Systems installed with {pve} 6.4 or later, EFI systems installed with |
444 | {pve} 5.4 or later] or plain `grub` as bootloader (see | |
445 | xref:sysboot[Host Bootloader]). You can check by running: | |
446 | ||
447 | ---- | |
448 | # proxmox-boot-tool status | |
449 | ---- | |
11a6e022 AL |
450 | |
451 | The first steps of copying the partition table, reissuing GUIDs and replacing | |
452 | the ZFS partition are the same. To make the system bootable from the new disk, | |
453 | different steps are needed which depend on the bootloader in use. | |
1748211a | 454 | |
eaefe614 FE |
455 | ---- |
456 | # sgdisk <healthy bootable device> -R <new device> | |
457 | # sgdisk -G <new device> | |
458 | # zpool replace -f <pool> <old zfs partition> <new zfs partition> | |
11a6e022 AL |
459 | ---- |
460 | ||
44aee838 | 461 | NOTE: Use the `zpool status -v` command to monitor how far the resilvering |
11a6e022 AL |
462 | process of the new disk has progressed. |
463 | ||
cb04e768 | 464 | .With `proxmox-boot-tool`: |
11a6e022 AL |
465 | |
466 | ---- | |
cb04e768 SI |
467 | # proxmox-boot-tool format <new disk's ESP> |
468 | # proxmox-boot-tool init <new disk's ESP> | |
eaefe614 | 469 | ---- |
0daaddbd FG |
470 | |
471 | NOTE: `ESP` stands for EFI System Partition, which is setup as partition #2 on | |
472 | bootable disks setup by the {pve} installer since version 5.4. For details, see | |
cb04e768 | 473 | xref:sysboot_proxmox_boot_setup[Setting up a new partition for use as synced ESP]. |
9ee94323 | 474 | |
69c2b2e5 | 475 | .With plain `grub`: |
11a6e022 AL |
476 | |
477 | ---- | |
478 | # grub-install <new disk> | |
479 | ---- | |
69c2b2e5 SI |
480 | NOTE: plain `grub` is only used on systems installed with {pve} 6.3 or earlier, |
481 | which have not been manually migrated to using `proxmox-boot-tool` yet. | |
482 | ||
9ee94323 | 483 | |
aa425868 FE |
484 | Configure E-Mail Notification |
485 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
9ee94323 | 486 | |
aa425868 FE |
487 | ZFS comes with an event daemon `ZED`, which monitors events generated by the ZFS |
488 | kernel module. The daemon can also send emails on ZFS events like pool errors. | |
489 | Newer ZFS packages ship the daemon in a separate `zfs-zed` package, which should | |
490 | already be installed by default in {pve}. | |
e280a948 | 491 | |
aa425868 FE |
492 | You can configure the daemon via the file `/etc/zfs/zed.d/zed.rc` with your |
493 | favorite editor. The required setting for email notification is | |
494 | `ZED_EMAIL_ADDR`, which is set to `root` by default. | |
9ee94323 | 495 | |
083adc34 | 496 | -------- |
9ee94323 | 497 | ZED_EMAIL_ADDR="root" |
083adc34 | 498 | -------- |
9ee94323 | 499 | |
8c1189b6 | 500 | Please note {pve} forwards mails to `root` to the email address |
9ee94323 DM |
501 | configured for the root user. |
502 | ||
9ee94323 | 503 | |
42449bdf | 504 | [[sysadmin_zfs_limit_memory_usage]] |
5eba0743 | 505 | Limit ZFS Memory Usage |
9ee94323 DM |
506 | ~~~~~~~~~~~~~~~~~~~~~~ |
507 | ||
9060abb9 TL |
508 | ZFS uses '50 %' of the host memory for the **A**daptive **R**eplacement |
509 | **C**ache (ARC) by default. Allocating enough memory for the ARC is crucial for | |
510 | IO performance, so reduce it with caution. As a general rule of thumb, allocate | |
511 | at least +2 GiB Base + 1 GiB/TiB-Storage+. For example, if you have a pool with | |
512 | +8 TiB+ of available storage space then you should use +10 GiB+ of memory for | |
513 | the ARC. | |
514 | ||
515 | You can change the ARC usage limit for the current boot (a reboot resets this | |
516 | change again) by writing to the +zfs_arc_max+ module parameter directly: | |
517 | ||
518 | ---- | |
519 | echo "$[10 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max | |
520 | ---- | |
521 | ||
522 | To *permanently change* the ARC limits, add the following line to | |
523 | `/etc/modprobe.d/zfs.conf`: | |
9ee94323 | 524 | |
5eba0743 FG |
525 | -------- |
526 | options zfs zfs_arc_max=8589934592 | |
527 | -------- | |
9ee94323 | 528 | |
9060abb9 | 529 | This example setting limits the usage to 8 GiB ('8 * 2^30^'). |
9ee94323 | 530 | |
beed14f8 FG |
531 | IMPORTANT: In case your desired +zfs_arc_max+ value is lower than or equal to |
532 | +zfs_arc_min+ (which defaults to 1/32 of the system memory), +zfs_arc_max+ will | |
533 | be ignored unless you also set +zfs_arc_min+ to at most +zfs_arc_max - 1+. | |
534 | ||
535 | ---- | |
536 | echo "$[8 * 1024*1024*1024 - 1]" >/sys/module/zfs/parameters/zfs_arc_min | |
537 | echo "$[8 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max | |
538 | ---- | |
539 | ||
540 | This example setting (temporarily) limits the usage to 8 GiB ('8 * 2^30^') on | |
541 | systems with more than 256 GiB of total memory, where simply setting | |
542 | +zfs_arc_max+ alone would not work. | |
543 | ||
9ee94323 DM |
544 | [IMPORTANT] |
545 | ==== | |
9060abb9 | 546 | If your root file system is ZFS, you must update your initramfs every |
5eba0743 | 547 | time this value changes: |
9ee94323 | 548 | |
eaefe614 | 549 | ---- |
abdfbbbb | 550 | # update-initramfs -u -k all |
eaefe614 | 551 | ---- |
9060abb9 TL |
552 | |
553 | You *must reboot* to activate these changes. | |
9ee94323 DM |
554 | ==== |
555 | ||
556 | ||
dc74fc63 | 557 | [[zfs_swap]] |
4128e7ff TL |
558 | SWAP on ZFS |
559 | ~~~~~~~~~~~ | |
9ee94323 | 560 | |
dc74fc63 | 561 | Swap-space created on a zvol may generate some troubles, like blocking the |
9ee94323 DM |
562 | server or generating a high IO load, often seen when starting a Backup |
563 | to an external Storage. | |
564 | ||
565 | We strongly recommend to use enough memory, so that you normally do not | |
dc74fc63 | 566 | run into low memory situations. Should you need or want to add swap, it is |
3a433e9b | 567 | preferred to create a partition on a physical disk and use it as a swap device. |
dc74fc63 SI |
568 | You can leave some space free for this purpose in the advanced options of the |
569 | installer. Additionally, you can lower the | |
8c1189b6 | 570 | ``swappiness'' value. A good value for servers is 10: |
9ee94323 | 571 | |
eaefe614 FE |
572 | ---- |
573 | # sysctl -w vm.swappiness=10 | |
574 | ---- | |
9ee94323 | 575 | |
8c1189b6 | 576 | To make the swappiness persistent, open `/etc/sysctl.conf` with |
9ee94323 DM |
577 | an editor of your choice and add the following line: |
578 | ||
083adc34 FG |
579 | -------- |
580 | vm.swappiness = 10 | |
581 | -------- | |
9ee94323 | 582 | |
8c1189b6 | 583 | .Linux kernel `swappiness` parameter values |
9ee94323 DM |
584 | [width="100%",cols="<m,2d",options="header"] |
585 | |=========================================================== | |
586 | | Value | Strategy | |
587 | | vm.swappiness = 0 | The kernel will swap only to avoid | |
588 | an 'out of memory' condition | |
589 | | vm.swappiness = 1 | Minimum amount of swapping without | |
590 | disabling it entirely. | |
591 | | vm.swappiness = 10 | This value is sometimes recommended to | |
592 | improve performance when sufficient memory exists in a system. | |
593 | | vm.swappiness = 60 | The default value. | |
594 | | vm.swappiness = 100 | The kernel will swap aggressively. | |
595 | |=========================================================== | |
cca0540e FG |
596 | |
597 | [[zfs_encryption]] | |
4128e7ff TL |
598 | Encrypted ZFS Datasets |
599 | ~~~~~~~~~~~~~~~~~~~~~~ | |
cca0540e | 600 | |
500e5ab3 ML |
601 | WARNING: Native ZFS encryption in {pve} is experimental. Known limitations and |
602 | issues include Replication with encrypted datasets | |
603 | footnote:[https://bugzilla.proxmox.com/show_bug.cgi?id=2350], | |
604 | as well as checksum errors when using Snapshots or ZVOLs. | |
605 | footnote:[https://github.com/openzfs/zfs/issues/11688] | |
606 | ||
cca0540e FG |
607 | ZFS on Linux version 0.8.0 introduced support for native encryption of |
608 | datasets. After an upgrade from previous ZFS on Linux versions, the encryption | |
229426eb | 609 | feature can be enabled per pool: |
cca0540e FG |
610 | |
611 | ---- | |
612 | # zpool get feature@encryption tank | |
613 | NAME PROPERTY VALUE SOURCE | |
614 | tank feature@encryption disabled local | |
615 | ||
616 | # zpool set feature@encryption=enabled | |
617 | ||
618 | # zpool get feature@encryption tank | |
619 | NAME PROPERTY VALUE SOURCE | |
620 | tank feature@encryption enabled local | |
621 | ---- | |
622 | ||
623 | WARNING: There is currently no support for booting from pools with encrypted | |
624 | datasets using Grub, and only limited support for automatically unlocking | |
625 | encrypted datasets on boot. Older versions of ZFS without encryption support | |
626 | will not be able to decrypt stored data. | |
627 | ||
628 | NOTE: It is recommended to either unlock storage datasets manually after | |
629 | booting, or to write a custom unit to pass the key material needed for | |
630 | unlocking on boot to `zfs load-key`. | |
631 | ||
632 | WARNING: Establish and test a backup procedure before enabling encryption of | |
5dfeeece | 633 | production data. If the associated key material/passphrase/keyfile has been |
cca0540e FG |
634 | lost, accessing the encrypted data is no longer possible. |
635 | ||
636 | Encryption needs to be setup when creating datasets/zvols, and is inherited by | |
637 | default to child datasets. For example, to create an encrypted dataset | |
638 | `tank/encrypted_data` and configure it as storage in {pve}, run the following | |
639 | commands: | |
640 | ||
641 | ---- | |
642 | # zfs create -o encryption=on -o keyformat=passphrase tank/encrypted_data | |
643 | Enter passphrase: | |
644 | Re-enter passphrase: | |
645 | ||
646 | # pvesm add zfspool encrypted_zfs -pool tank/encrypted_data | |
647 | ---- | |
648 | ||
649 | All guest volumes/disks create on this storage will be encrypted with the | |
650 | shared key material of the parent dataset. | |
651 | ||
652 | To actually use the storage, the associated key material needs to be loaded | |
7353437b | 653 | and the dataset needs to be mounted. This can be done in one step with: |
cca0540e FG |
654 | |
655 | ---- | |
7353437b | 656 | # zfs mount -l tank/encrypted_data |
cca0540e FG |
657 | Enter passphrase for 'tank/encrypted_data': |
658 | ---- | |
659 | ||
660 | It is also possible to use a (random) keyfile instead of prompting for a | |
661 | passphrase by setting the `keylocation` and `keyformat` properties, either at | |
229426eb | 662 | creation time or with `zfs change-key` on existing datasets: |
cca0540e FG |
663 | |
664 | ---- | |
665 | # dd if=/dev/urandom of=/path/to/keyfile bs=32 count=1 | |
666 | ||
667 | # zfs change-key -o keyformat=raw -o keylocation=file:///path/to/keyfile tank/encrypted_data | |
668 | ---- | |
669 | ||
670 | WARNING: When using a keyfile, special care needs to be taken to secure the | |
671 | keyfile against unauthorized access or accidental loss. Without the keyfile, it | |
672 | is not possible to access the plaintext data! | |
673 | ||
674 | A guest volume created underneath an encrypted dataset will have its | |
675 | `encryptionroot` property set accordingly. The key material only needs to be | |
676 | loaded once per encryptionroot to be available to all encrypted datasets | |
677 | underneath it. | |
678 | ||
679 | See the `encryptionroot`, `encryption`, `keylocation`, `keyformat` and | |
680 | `keystatus` properties, the `zfs load-key`, `zfs unload-key` and `zfs | |
681 | change-key` commands and the `Encryption` section from `man zfs` for more | |
682 | details and advanced usage. | |
68029ec8 FE |
683 | |
684 | ||
e06707f2 FE |
685 | [[zfs_compression]] |
686 | Compression in ZFS | |
687 | ~~~~~~~~~~~~~~~~~~ | |
688 | ||
689 | When compression is enabled on a dataset, ZFS tries to compress all *new* | |
690 | blocks before writing them and decompresses them on reading. Already | |
691 | existing data will not be compressed retroactively. | |
692 | ||
693 | You can enable compression with: | |
694 | ||
695 | ---- | |
696 | # zfs set compression=<algorithm> <dataset> | |
697 | ---- | |
698 | ||
699 | We recommend using the `lz4` algorithm, because it adds very little CPU | |
700 | overhead. Other algorithms like `lzjb` and `gzip-N`, where `N` is an | |
701 | integer from `1` (fastest) to `9` (best compression ratio), are also | |
702 | available. Depending on the algorithm and how compressible the data is, | |
703 | having compression enabled can even increase I/O performance. | |
704 | ||
705 | You can disable compression at any time with: | |
706 | ||
707 | ---- | |
708 | # zfs set compression=off <dataset> | |
709 | ---- | |
710 | ||
711 | Again, only new blocks will be affected by this change. | |
712 | ||
713 | ||
42449bdf | 714 | [[sysadmin_zfs_special_device]] |
68029ec8 FE |
715 | ZFS Special Device |
716 | ~~~~~~~~~~~~~~~~~~ | |
717 | ||
718 | Since version 0.8.0 ZFS supports `special` devices. A `special` device in a | |
719 | pool is used to store metadata, deduplication tables, and optionally small | |
720 | file blocks. | |
721 | ||
722 | A `special` device can improve the speed of a pool consisting of slow spinning | |
51e544b6 TL |
723 | hard disks with a lot of metadata changes. For example workloads that involve |
724 | creating, updating or deleting a large number of files will benefit from the | |
725 | presence of a `special` device. ZFS datasets can also be configured to store | |
726 | whole small files on the `special` device which can further improve the | |
727 | performance. Use fast SSDs for the `special` device. | |
68029ec8 FE |
728 | |
729 | IMPORTANT: The redundancy of the `special` device should match the one of the | |
730 | pool, since the `special` device is a point of failure for the whole pool. | |
731 | ||
732 | WARNING: Adding a `special` device to a pool cannot be undone! | |
733 | ||
734 | .Create a pool with `special` device and RAID-1: | |
735 | ||
eaefe614 FE |
736 | ---- |
737 | # zpool create -f -o ashift=12 <pool> mirror <device1> <device2> special mirror <device3> <device4> | |
738 | ---- | |
68029ec8 FE |
739 | |
740 | .Add a `special` device to an existing pool with RAID-1: | |
741 | ||
eaefe614 FE |
742 | ---- |
743 | # zpool add <pool> special mirror <device1> <device2> | |
744 | ---- | |
68029ec8 FE |
745 | |
746 | ZFS datasets expose the `special_small_blocks=<size>` property. `size` can be | |
747 | `0` to disable storing small file blocks on the `special` device or a power of | |
9deec2e2 | 748 | two in the range between `512B` to `1M`. After setting the property new file |
68029ec8 FE |
749 | blocks smaller than `size` will be allocated on the `special` device. |
750 | ||
751 | IMPORTANT: If the value for `special_small_blocks` is greater than or equal to | |
51e544b6 TL |
752 | the `recordsize` (default `128K`) of the dataset, *all* data will be written to |
753 | the `special` device, so be careful! | |
68029ec8 FE |
754 | |
755 | Setting the `special_small_blocks` property on a pool will change the default | |
756 | value of that property for all child ZFS datasets (for example all containers | |
757 | in the pool will opt in for small file blocks). | |
758 | ||
51e544b6 | 759 | .Opt in for all file smaller than 4K-blocks pool-wide: |
68029ec8 | 760 | |
eaefe614 FE |
761 | ---- |
762 | # zfs set special_small_blocks=4K <pool> | |
763 | ---- | |
68029ec8 FE |
764 | |
765 | .Opt in for small file blocks for a single dataset: | |
766 | ||
eaefe614 FE |
767 | ---- |
768 | # zfs set special_small_blocks=4K <pool>/<filesystem> | |
769 | ---- | |
68029ec8 FE |
770 | |
771 | .Opt out from small file blocks for a single dataset: | |
772 | ||
eaefe614 FE |
773 | ---- |
774 | # zfs set special_small_blocks=0 <pool>/<filesystem> | |
775 | ---- | |
18d0d68e SI |
776 | |
777 | [[sysadmin_zfs_features]] | |
778 | ZFS Pool Features | |
779 | ~~~~~~~~~~~~~~~~~ | |
780 | ||
781 | Changes to the on-disk format in ZFS are only made between major version changes | |
782 | and are specified through *features*. All features, as well as the general | |
783 | mechanism are well documented in the `zpool-features(5)` manpage. | |
784 | ||
785 | Since enabling new features can render a pool not importable by an older version | |
786 | of ZFS, this needs to be done actively by the administrator, by running | |
787 | `zpool upgrade` on the pool (see the `zpool-upgrade(8)` manpage). | |
788 | ||
789 | Unless you need to use one of the new features, there is no upside to enabling | |
790 | them. | |
791 | ||
792 | In fact, there are some downsides to enabling new features: | |
793 | ||
794 | * A system with root on ZFS, that still boots using `grub` will become | |
795 | unbootable if a new feature is active on the rpool, due to the incompatible | |
796 | implementation of ZFS in grub. | |
797 | * The system will not be able to import any upgraded pool when booted with an | |
798 | older kernel, which still ships with the old ZFS modules. | |
799 | * Booting an older {pve} ISO to repair a non-booting system will likewise not | |
800 | work. | |
801 | ||
27adc096 TL |
802 | IMPORTANT: Do *not* upgrade your rpool if your system is still booted with |
803 | `grub`, as this will render your system unbootable. This includes systems | |
804 | installed before {pve} 5.4, and systems booting with legacy BIOS boot (see | |
18d0d68e SI |
805 | xref:sysboot_determine_bootloader_used[how to determine the bootloader]). |
806 | ||
27adc096 | 807 | .Enable new features for a ZFS pool: |
18d0d68e SI |
808 | ---- |
809 | # zpool upgrade <pool> | |
810 | ---- |