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0235c741 | 1 | [[chapter_zfs]] |
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2 | ZFS on Linux |
3 | ------------ | |
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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 | ||
35 | * Various raid levels: RAID0, RAID1, RAID10, RAIDZ-1, RAIDZ-2 and RAIDZ-3 | |
36 | ||
37 | * Can use SSD for cache | |
38 | ||
39 | * Self healing | |
40 | ||
41 | * Continuous integrity checking | |
42 | ||
43 | * Designed for high storage capacities | |
44 | ||
45 | * Protection against data corruption | |
46 | ||
47 | * Asynchronous replication over network | |
48 | ||
49 | * Open Source | |
50 | ||
51 | * Encryption | |
52 | ||
53 | * ... | |
54 | ||
55 | ||
56 | Hardware | |
57 | ~~~~~~~~ | |
58 | ||
59 | ZFS depends heavily on memory, so you need at least 8GB to start. In | |
60 | practice, use as much you can get for your hardware/budget. To prevent | |
61 | data corruption, we recommend the use of high quality ECC RAM. | |
62 | ||
d48bdcf2 | 63 | If you use a dedicated cache and/or log disk, you should use an |
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64 | enterprise class SSD (e.g. Intel SSD DC S3700 Series). This can |
65 | increase the overall performance significantly. | |
66 | ||
5eba0743 | 67 | IMPORTANT: Do not use ZFS on top of hardware controller which has its |
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68 | own cache management. ZFS needs to directly communicate with disks. An |
69 | HBA adapter is the way to go, or something like LSI controller flashed | |
8c1189b6 | 70 | in ``IT'' mode. |
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71 | |
72 | If you are experimenting with an installation of {pve} inside a VM | |
8c1189b6 | 73 | (Nested Virtualization), don't use `virtio` for disks of that VM, |
9ee94323 | 74 | since they are not supported by ZFS. Use IDE or SCSI instead (works |
8c1189b6 | 75 | also with `virtio` SCSI controller type). |
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76 | |
77 | ||
5eba0743 | 78 | Installation as Root File System |
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79 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
80 | ||
81 | When you install using the {pve} installer, you can choose ZFS for the | |
82 | root file system. You need to select the RAID type at installation | |
83 | time: | |
84 | ||
85 | [horizontal] | |
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86 | RAID0:: Also called ``striping''. The capacity of such volume is the sum |
87 | of the capacities of all disks. But RAID0 does not add any redundancy, | |
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88 | so the failure of a single drive makes the volume unusable. |
89 | ||
8c1189b6 | 90 | RAID1:: Also called ``mirroring''. Data is written identically to all |
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91 | disks. This mode requires at least 2 disks with the same size. The |
92 | resulting capacity is that of a single disk. | |
93 | ||
94 | RAID10:: A combination of RAID0 and RAID1. Requires at least 4 disks. | |
95 | ||
96 | RAIDZ-1:: A variation on RAID-5, single parity. Requires at least 3 disks. | |
97 | ||
98 | RAIDZ-2:: A variation on RAID-5, double parity. Requires at least 4 disks. | |
99 | ||
100 | RAIDZ-3:: A variation on RAID-5, triple parity. Requires at least 5 disks. | |
101 | ||
102 | The installer automatically partitions the disks, creates a ZFS pool | |
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103 | called `rpool`, and installs the root file system on the ZFS subvolume |
104 | `rpool/ROOT/pve-1`. | |
9ee94323 | 105 | |
8c1189b6 | 106 | Another subvolume called `rpool/data` is created to store VM |
9ee94323 | 107 | images. In order to use that with the {pve} tools, the installer |
8c1189b6 | 108 | creates the following configuration entry in `/etc/pve/storage.cfg`: |
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109 | |
110 | ---- | |
111 | zfspool: local-zfs | |
112 | pool rpool/data | |
113 | sparse | |
114 | content images,rootdir | |
115 | ---- | |
116 | ||
117 | After installation, you can view your ZFS pool status using the | |
8c1189b6 | 118 | `zpool` command: |
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119 | |
120 | ---- | |
121 | # zpool status | |
122 | pool: rpool | |
123 | state: ONLINE | |
124 | scan: none requested | |
125 | config: | |
126 | ||
127 | NAME STATE READ WRITE CKSUM | |
128 | rpool ONLINE 0 0 0 | |
129 | mirror-0 ONLINE 0 0 0 | |
130 | sda2 ONLINE 0 0 0 | |
131 | sdb2 ONLINE 0 0 0 | |
132 | mirror-1 ONLINE 0 0 0 | |
133 | sdc ONLINE 0 0 0 | |
134 | sdd ONLINE 0 0 0 | |
135 | ||
136 | errors: No known data errors | |
137 | ---- | |
138 | ||
8c1189b6 | 139 | The `zfs` command is used configure and manage your ZFS file |
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140 | systems. The following command lists all file systems after |
141 | installation: | |
142 | ||
143 | ---- | |
144 | # zfs list | |
145 | NAME USED AVAIL REFER MOUNTPOINT | |
146 | rpool 4.94G 7.68T 96K /rpool | |
147 | rpool/ROOT 702M 7.68T 96K /rpool/ROOT | |
148 | rpool/ROOT/pve-1 702M 7.68T 702M / | |
149 | rpool/data 96K 7.68T 96K /rpool/data | |
150 | rpool/swap 4.25G 7.69T 64K - | |
151 | ---- | |
152 | ||
153 | ||
154 | Bootloader | |
155 | ~~~~~~~~~~ | |
156 | ||
1748211a SI |
157 | Depending on whether the system is booted in EFI or legacy BIOS mode the |
158 | {pve} installer sets up either `grub` or `systemd-boot` as main bootloader. | |
69055103 | 159 | See the chapter on xref:sysboot[{pve} host bootladers] for details. |
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160 | |
161 | ||
162 | ZFS Administration | |
163 | ~~~~~~~~~~~~~~~~~~ | |
164 | ||
165 | This section gives you some usage examples for common tasks. ZFS | |
166 | itself is really powerful and provides many options. The main commands | |
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167 | to manage ZFS are `zfs` and `zpool`. Both commands come with great |
168 | manual pages, which can be read with: | |
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169 | |
170 | ---- | |
171 | # man zpool | |
172 | # man zfs | |
173 | ----- | |
174 | ||
5eba0743 | 175 | .Create a new zpool |
9ee94323 | 176 | |
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177 | To create a new pool, at least one disk is needed. The `ashift` should |
178 | have the same sector-size (2 power of `ashift`) or larger as the | |
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179 | underlying disk. |
180 | ||
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181 | ---- |
182 | # zpool create -f -o ashift=12 <pool> <device> | |
183 | ---- | |
9ee94323 | 184 | |
e06707f2 | 185 | To activate compression (see section <<zfs_compression,Compression in ZFS>>): |
9ee94323 | 186 | |
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187 | ---- |
188 | # zfs set compression=lz4 <pool> | |
189 | ---- | |
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190 | |
191 | .Create a new pool with RAID-0 | |
192 | ||
dc2d00a0 | 193 | Minimum 1 disk |
9ee94323 | 194 | |
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195 | ---- |
196 | # zpool create -f -o ashift=12 <pool> <device1> <device2> | |
197 | ---- | |
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198 | |
199 | .Create a new pool with RAID-1 | |
200 | ||
dc2d00a0 | 201 | Minimum 2 disks |
9ee94323 | 202 | |
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203 | ---- |
204 | # zpool create -f -o ashift=12 <pool> mirror <device1> <device2> | |
205 | ---- | |
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206 | |
207 | .Create a new pool with RAID-10 | |
208 | ||
dc2d00a0 | 209 | Minimum 4 disks |
9ee94323 | 210 | |
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211 | ---- |
212 | # zpool create -f -o ashift=12 <pool> mirror <device1> <device2> mirror <device3> <device4> | |
213 | ---- | |
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214 | |
215 | .Create a new pool with RAIDZ-1 | |
216 | ||
dc2d00a0 | 217 | Minimum 3 disks |
9ee94323 | 218 | |
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219 | ---- |
220 | # zpool create -f -o ashift=12 <pool> raidz1 <device1> <device2> <device3> | |
221 | ---- | |
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222 | |
223 | .Create a new pool with RAIDZ-2 | |
224 | ||
dc2d00a0 | 225 | Minimum 4 disks |
9ee94323 | 226 | |
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227 | ---- |
228 | # zpool create -f -o ashift=12 <pool> raidz2 <device1> <device2> <device3> <device4> | |
229 | ---- | |
9ee94323 | 230 | |
5eba0743 | 231 | .Create a new pool with cache (L2ARC) |
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232 | |
233 | It is possible to use a dedicated cache drive partition to increase | |
234 | the performance (use SSD). | |
235 | ||
8c1189b6 | 236 | As `<device>` it is possible to use more devices, like it's shown in |
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237 | "Create a new pool with RAID*". |
238 | ||
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239 | ---- |
240 | # zpool create -f -o ashift=12 <pool> <device> cache <cache_device> | |
241 | ---- | |
9ee94323 | 242 | |
5eba0743 | 243 | .Create a new pool with log (ZIL) |
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244 | |
245 | It is possible to use a dedicated cache drive partition to increase | |
246 | the performance(SSD). | |
247 | ||
8c1189b6 | 248 | As `<device>` it is possible to use more devices, like it's shown in |
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249 | "Create a new pool with RAID*". |
250 | ||
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251 | ---- |
252 | # zpool create -f -o ashift=12 <pool> <device> log <log_device> | |
253 | ---- | |
9ee94323 | 254 | |
5eba0743 | 255 | .Add cache and log to an existing pool |
9ee94323 | 256 | |
5dfeeece | 257 | If you have a pool without cache and log. First partition the SSD in |
8c1189b6 | 258 | 2 partition with `parted` or `gdisk` |
9ee94323 | 259 | |
e300cf7d | 260 | IMPORTANT: Always use GPT partition tables. |
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261 | |
262 | The maximum size of a log device should be about half the size of | |
263 | physical memory, so this is usually quite small. The rest of the SSD | |
5eba0743 | 264 | can be used as cache. |
9ee94323 | 265 | |
eaefe614 | 266 | ---- |
237007eb | 267 | # zpool add -f <pool> log <device-part1> cache <device-part2> |
eaefe614 | 268 | ---- |
9ee94323 | 269 | |
5eba0743 | 270 | .Changing a failed device |
9ee94323 | 271 | |
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272 | ---- |
273 | # zpool replace -f <pool> <old device> <new device> | |
274 | ---- | |
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275 | |
276 | .Changing a failed bootable device when using systemd-boot | |
277 | ||
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278 | ---- |
279 | # sgdisk <healthy bootable device> -R <new device> | |
280 | # sgdisk -G <new device> | |
281 | # zpool replace -f <pool> <old zfs partition> <new zfs partition> | |
282 | # pve-efiboot-tool format <new disk's ESP> | |
283 | # pve-efiboot-tool init <new disk's ESP> | |
284 | ---- | |
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285 | |
286 | NOTE: `ESP` stands for EFI System Partition, which is setup as partition #2 on | |
287 | bootable disks setup by the {pve} installer since version 5.4. For details, see | |
288 | xref:sysboot_systemd_boot_setup[Setting up a new partition for use as synced ESP]. | |
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289 | |
290 | ||
291 | Activate E-Mail Notification | |
292 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
293 | ||
294 | ZFS comes with an event daemon, which monitors events generated by the | |
5eba0743 | 295 | ZFS kernel module. The daemon can also send emails on ZFS events like |
5dfeeece | 296 | pool errors. Newer ZFS packages ship the daemon in a separate package, |
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297 | and you can install it using `apt-get`: |
298 | ||
299 | ---- | |
300 | # apt-get install zfs-zed | |
301 | ---- | |
9ee94323 | 302 | |
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303 | To activate the daemon it is necessary to edit `/etc/zfs/zed.d/zed.rc` with your |
304 | favourite editor, and uncomment the `ZED_EMAIL_ADDR` setting: | |
9ee94323 | 305 | |
083adc34 | 306 | -------- |
9ee94323 | 307 | ZED_EMAIL_ADDR="root" |
083adc34 | 308 | -------- |
9ee94323 | 309 | |
8c1189b6 | 310 | Please note {pve} forwards mails to `root` to the email address |
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311 | configured for the root user. |
312 | ||
8c1189b6 | 313 | IMPORTANT: The only setting that is required is `ZED_EMAIL_ADDR`. All |
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314 | other settings are optional. |
315 | ||
316 | ||
5eba0743 | 317 | Limit ZFS Memory Usage |
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318 | ~~~~~~~~~~~~~~~~~~~~~~ |
319 | ||
5eba0743 | 320 | It is good to use at most 50 percent (which is the default) of the |
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321 | system memory for ZFS ARC to prevent performance shortage of the |
322 | host. Use your preferred editor to change the configuration in | |
8c1189b6 | 323 | `/etc/modprobe.d/zfs.conf` and insert: |
9ee94323 | 324 | |
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325 | -------- |
326 | options zfs zfs_arc_max=8589934592 | |
327 | -------- | |
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328 | |
329 | This example setting limits the usage to 8GB. | |
330 | ||
331 | [IMPORTANT] | |
332 | ==== | |
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333 | If your root file system is ZFS you must update your initramfs every |
334 | time this value changes: | |
9ee94323 | 335 | |
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336 | ---- |
337 | # update-initramfs -u | |
338 | ---- | |
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339 | ==== |
340 | ||
341 | ||
dc74fc63 | 342 | [[zfs_swap]] |
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343 | SWAP on ZFS |
344 | ~~~~~~~~~~~ | |
9ee94323 | 345 | |
dc74fc63 | 346 | Swap-space created on a zvol may generate some troubles, like blocking the |
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347 | server or generating a high IO load, often seen when starting a Backup |
348 | to an external Storage. | |
349 | ||
350 | We strongly recommend to use enough memory, so that you normally do not | |
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351 | run into low memory situations. Should you need or want to add swap, it is |
352 | preferred to create a partition on a physical disk and use it as swapdevice. | |
353 | You can leave some space free for this purpose in the advanced options of the | |
354 | installer. Additionally, you can lower the | |
8c1189b6 | 355 | ``swappiness'' value. A good value for servers is 10: |
9ee94323 | 356 | |
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357 | ---- |
358 | # sysctl -w vm.swappiness=10 | |
359 | ---- | |
9ee94323 | 360 | |
8c1189b6 | 361 | To make the swappiness persistent, open `/etc/sysctl.conf` with |
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362 | an editor of your choice and add the following line: |
363 | ||
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364 | -------- |
365 | vm.swappiness = 10 | |
366 | -------- | |
9ee94323 | 367 | |
8c1189b6 | 368 | .Linux kernel `swappiness` parameter values |
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369 | [width="100%",cols="<m,2d",options="header"] |
370 | |=========================================================== | |
371 | | Value | Strategy | |
372 | | vm.swappiness = 0 | The kernel will swap only to avoid | |
373 | an 'out of memory' condition | |
374 | | vm.swappiness = 1 | Minimum amount of swapping without | |
375 | disabling it entirely. | |
376 | | vm.swappiness = 10 | This value is sometimes recommended to | |
377 | improve performance when sufficient memory exists in a system. | |
378 | | vm.swappiness = 60 | The default value. | |
379 | | vm.swappiness = 100 | The kernel will swap aggressively. | |
380 | |=========================================================== | |
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381 | |
382 | [[zfs_encryption]] | |
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383 | Encrypted ZFS Datasets |
384 | ~~~~~~~~~~~~~~~~~~~~~~ | |
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385 | |
386 | ZFS on Linux version 0.8.0 introduced support for native encryption of | |
387 | datasets. After an upgrade from previous ZFS on Linux versions, the encryption | |
229426eb | 388 | feature can be enabled per pool: |
cca0540e FG |
389 | |
390 | ---- | |
391 | # zpool get feature@encryption tank | |
392 | NAME PROPERTY VALUE SOURCE | |
393 | tank feature@encryption disabled local | |
394 | ||
395 | # zpool set feature@encryption=enabled | |
396 | ||
397 | # zpool get feature@encryption tank | |
398 | NAME PROPERTY VALUE SOURCE | |
399 | tank feature@encryption enabled local | |
400 | ---- | |
401 | ||
402 | WARNING: There is currently no support for booting from pools with encrypted | |
403 | datasets using Grub, and only limited support for automatically unlocking | |
404 | encrypted datasets on boot. Older versions of ZFS without encryption support | |
405 | will not be able to decrypt stored data. | |
406 | ||
407 | NOTE: It is recommended to either unlock storage datasets manually after | |
408 | booting, or to write a custom unit to pass the key material needed for | |
409 | unlocking on boot to `zfs load-key`. | |
410 | ||
411 | WARNING: Establish and test a backup procedure before enabling encryption of | |
5dfeeece | 412 | production data. If the associated key material/passphrase/keyfile has been |
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413 | lost, accessing the encrypted data is no longer possible. |
414 | ||
415 | Encryption needs to be setup when creating datasets/zvols, and is inherited by | |
416 | default to child datasets. For example, to create an encrypted dataset | |
417 | `tank/encrypted_data` and configure it as storage in {pve}, run the following | |
418 | commands: | |
419 | ||
420 | ---- | |
421 | # zfs create -o encryption=on -o keyformat=passphrase tank/encrypted_data | |
422 | Enter passphrase: | |
423 | Re-enter passphrase: | |
424 | ||
425 | # pvesm add zfspool encrypted_zfs -pool tank/encrypted_data | |
426 | ---- | |
427 | ||
428 | All guest volumes/disks create on this storage will be encrypted with the | |
429 | shared key material of the parent dataset. | |
430 | ||
431 | To actually use the storage, the associated key material needs to be loaded | |
432 | with `zfs load-key`: | |
433 | ||
434 | ---- | |
435 | # zfs load-key tank/encrypted_data | |
436 | Enter passphrase for 'tank/encrypted_data': | |
437 | ---- | |
438 | ||
439 | It is also possible to use a (random) keyfile instead of prompting for a | |
440 | passphrase by setting the `keylocation` and `keyformat` properties, either at | |
229426eb | 441 | creation time or with `zfs change-key` on existing datasets: |
cca0540e FG |
442 | |
443 | ---- | |
444 | # dd if=/dev/urandom of=/path/to/keyfile bs=32 count=1 | |
445 | ||
446 | # zfs change-key -o keyformat=raw -o keylocation=file:///path/to/keyfile tank/encrypted_data | |
447 | ---- | |
448 | ||
449 | WARNING: When using a keyfile, special care needs to be taken to secure the | |
450 | keyfile against unauthorized access or accidental loss. Without the keyfile, it | |
451 | is not possible to access the plaintext data! | |
452 | ||
453 | A guest volume created underneath an encrypted dataset will have its | |
454 | `encryptionroot` property set accordingly. The key material only needs to be | |
455 | loaded once per encryptionroot to be available to all encrypted datasets | |
456 | underneath it. | |
457 | ||
458 | See the `encryptionroot`, `encryption`, `keylocation`, `keyformat` and | |
459 | `keystatus` properties, the `zfs load-key`, `zfs unload-key` and `zfs | |
460 | change-key` commands and the `Encryption` section from `man zfs` for more | |
461 | details and advanced usage. | |
68029ec8 FE |
462 | |
463 | ||
e06707f2 FE |
464 | [[zfs_compression]] |
465 | Compression in ZFS | |
466 | ~~~~~~~~~~~~~~~~~~ | |
467 | ||
468 | When compression is enabled on a dataset, ZFS tries to compress all *new* | |
469 | blocks before writing them and decompresses them on reading. Already | |
470 | existing data will not be compressed retroactively. | |
471 | ||
472 | You can enable compression with: | |
473 | ||
474 | ---- | |
475 | # zfs set compression=<algorithm> <dataset> | |
476 | ---- | |
477 | ||
478 | We recommend using the `lz4` algorithm, because it adds very little CPU | |
479 | overhead. Other algorithms like `lzjb` and `gzip-N`, where `N` is an | |
480 | integer from `1` (fastest) to `9` (best compression ratio), are also | |
481 | available. Depending on the algorithm and how compressible the data is, | |
482 | having compression enabled can even increase I/O performance. | |
483 | ||
484 | You can disable compression at any time with: | |
485 | ||
486 | ---- | |
487 | # zfs set compression=off <dataset> | |
488 | ---- | |
489 | ||
490 | Again, only new blocks will be affected by this change. | |
491 | ||
492 | ||
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493 | ZFS Special Device |
494 | ~~~~~~~~~~~~~~~~~~ | |
495 | ||
496 | Since version 0.8.0 ZFS supports `special` devices. A `special` device in a | |
497 | pool is used to store metadata, deduplication tables, and optionally small | |
498 | file blocks. | |
499 | ||
500 | A `special` device can improve the speed of a pool consisting of slow spinning | |
51e544b6 TL |
501 | hard disks with a lot of metadata changes. For example workloads that involve |
502 | creating, updating or deleting a large number of files will benefit from the | |
503 | presence of a `special` device. ZFS datasets can also be configured to store | |
504 | whole small files on the `special` device which can further improve the | |
505 | performance. Use fast SSDs for the `special` device. | |
68029ec8 FE |
506 | |
507 | IMPORTANT: The redundancy of the `special` device should match the one of the | |
508 | pool, since the `special` device is a point of failure for the whole pool. | |
509 | ||
510 | WARNING: Adding a `special` device to a pool cannot be undone! | |
511 | ||
512 | .Create a pool with `special` device and RAID-1: | |
513 | ||
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514 | ---- |
515 | # zpool create -f -o ashift=12 <pool> mirror <device1> <device2> special mirror <device3> <device4> | |
516 | ---- | |
68029ec8 FE |
517 | |
518 | .Add a `special` device to an existing pool with RAID-1: | |
519 | ||
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520 | ---- |
521 | # zpool add <pool> special mirror <device1> <device2> | |
522 | ---- | |
68029ec8 FE |
523 | |
524 | ZFS datasets expose the `special_small_blocks=<size>` property. `size` can be | |
525 | `0` to disable storing small file blocks on the `special` device or a power of | |
526 | two in the range between `512B` to `128K`. After setting the property new file | |
527 | blocks smaller than `size` will be allocated on the `special` device. | |
528 | ||
529 | IMPORTANT: If the value for `special_small_blocks` is greater than or equal to | |
51e544b6 TL |
530 | the `recordsize` (default `128K`) of the dataset, *all* data will be written to |
531 | the `special` device, so be careful! | |
68029ec8 FE |
532 | |
533 | Setting the `special_small_blocks` property on a pool will change the default | |
534 | value of that property for all child ZFS datasets (for example all containers | |
535 | in the pool will opt in for small file blocks). | |
536 | ||
51e544b6 | 537 | .Opt in for all file smaller than 4K-blocks pool-wide: |
68029ec8 | 538 | |
eaefe614 FE |
539 | ---- |
540 | # zfs set special_small_blocks=4K <pool> | |
541 | ---- | |
68029ec8 FE |
542 | |
543 | .Opt in for small file blocks for a single dataset: | |
544 | ||
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545 | ---- |
546 | # zfs set special_small_blocks=4K <pool>/<filesystem> | |
547 | ---- | |
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548 | |
549 | .Opt out from small file blocks for a single dataset: | |
550 | ||
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551 | ---- |
552 | # zfs set special_small_blocks=0 <pool>/<filesystem> | |
553 | ---- |