Zfs

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ZFS - Zettabyte Filesystem

Beginning ZFS instances

There are only two commmands to interact with ZFS.

zpool: used to create a ZFS vdev (virtual device).  vdevs are composed of physical devices.  
zfs: used to create/interact with a ZFS dataset.  ZFS datasets are akin to logical volumes
# zpool creation syntax
zpool create <poolname> <vdev(s)> 
# Create a zpool of six raidz2 vdevs, each with six drives.  Includes two SSDs to used as a mirrored SLOG and one SSD as an L2ARC read cache.  (example commmand was run on qof) 
zpool create ex9 raidz2 sda sdb sdc sdd sde sdf raidz2 sdg sdh sdi sdj sdk sdl raidz2 sdm sdn sdo sdp sdq sdr raidz2 sds sdt sdu sdv sdw sdx raidz2 sdy sdz sdaa sdab sdac sdad raidz2 sdae sdaf sdag sdah sdai sdaj log mirror ata-INTEL_SSDSC2KG480G7_BTYM740603E0480BGN ata-INTEL_SSDSC2KG480G7_BTYM7406019K480BGN cache ata-INTEL_SSDSC2KG480G7_BTYM740602GN480BGN
 [root@qof ~]# zpool status
 pool: ex9
 state: ONLINE
 scan: none requested
 config:
 NAME                                            STATE     READ WRITE CKSUM
 ex9                                             ONLINE       0     0     0
 raidz2-0                                      ONLINE       0     0     0
   sda                                         ONLINE       0     0     0
   sdb                                         ONLINE       0     0     0
   sdc                                         ONLINE       0     0     0
   sdd                                         ONLINE       0     0     0
   sde                                         ONLINE       0     0     0
   sdf                                         ONLINE       0     0     0
 raidz2-1                                      ONLINE       0     0     0
   sdg                                         ONLINE       0     0     0
   sdh                                         ONLINE       0     0     0
   sdi                                         ONLINE       0     0     0
   sdj                                         ONLINE       0     0     0
   sdk                                         ONLINE       0     0     0
   sdl                                         ONLINE       0     0     0
 raidz2-2                                      ONLINE       0     0     0
   sdm                                         ONLINE       0     0     0
   sdn                                         ONLINE       0     0     0
   sdo                                         ONLINE       0     0     0
   sdp                                         ONLINE       0     0     0
   sdq                                         ONLINE       0     0     0
   sdr                                         ONLINE       0     0     0
 raidz2-3                                      ONLINE       0     0     0
   sds                                         ONLINE       0     0     0
   sdt                                         ONLINE       0     0     0
   sdu                                         ONLINE       0     0     0
   sdv                                         ONLINE       0     0     0
   sdw                                         ONLINE       0     0     0
   sdx                                         ONLINE       0     0     0
 raidz2-4                                      ONLINE       0     0     0
   sdy                                         ONLINE       0     0     0
   sdz                                         ONLINE       0     0     0
   sdaa                                        ONLINE       0     0     0
   sdab                                        ONLINE       0     0     0
   sdac                                        ONLINE       0     0     0
   sdad                                        ONLINE       0     0     0
 raidz2-5                                      ONLINE       0     0     0
   sdae                                        ONLINE       0     0     0
   sdaf                                        ONLINE       0     0     0
   sdag                                        ONLINE       0     0     0
   sdah                                        ONLINE       0     0     0
   sdai                                        ONLINE       0     0     0
   sdaj                                        ONLINE       0     0     0
 logs
 mirror-6                                      ONLINE       0     0     0
   ata-INTEL_SSDSC2KG480G7_BTYM740603E0480BGN  ONLINE       0     0     0
   ata-INTEL_SSDSC2KG480G7_BTYM7406019K480BGN  ONLINE       0     0     0
 cache
 ata-INTEL_SSDSC2KG480G7_BTYM740602GN480BGN    ONLINE       0     0     0

Adding a zfs filesystem:

Using qof as an example, I will create a child filesystem under ex9 named archive that will be mounted under /export/ex9/archive. This archive will be used to backup user data.

-bash-4.2$ zfs list
NAME          USED  AVAIL  REFER  MOUNTPOINT
ex9          2.39T   249T  2.39T  /export/ex9
-bash-4.2$ sudo zfs create -o mountpoint=/export/ex9/archive ex9/archive 
-bash-4.2$ zfs list
NAME          USED  AVAIL  REFER  MOUNTPOINT
ex9          2.39T   249T  2.39T  /export/ex9
ex9/archive   192K   249T   192K  /export/ex9/archive

Adding L2ARC Read Cache to a zpool

# Look for available SSDs in /dev/disk/by-id/
# Choose an available SSD to use for read cache.  Then decide which pool you want to put the cache on. 
Syntax: zpool add <zpool name> <cache/log> <path to disk>
$ sudo zpool add ex6 cache /dev/disk/by-id/ata-INTEL_SSDSC2KG480G7_BTYM72830AV6480BGN

Tuning ZFS options

 # stores extended attributes as system attributes to improve performance
 $ zfs xattr=sa <zfs dataset name> 
 
 # Turn on ZFS lz4 compression.  Use this for compressible dataset such as many files with text 
 $ zfs set compression=lz4 <zfs dataset name> 
 
 # Turn off access time for improved disk performance (so that the OS doesn't write a new time every time a file is accessed)
 $ zfs set atime=off <zfs dataset name>
 NOTE: ZFS performance degrades tremendously when the zpool is over 80% used.  To avoid this, I have set a quota to 80% of the 248TB in qof/nfs-ex9.
 # To set a quota of 200TB on ZFS dataset:
 $ zfs set quota=200T <zfs dataset>
 # To remove a quota from a ZFS dataset:
 $ zfs set quota=none <zfs dataset>

By default, ZFS pools/mounts do not have ACLs active.

 # to active access control lists on a zpool
 $ sudo zfs set acltype=posixacl <pool name>

situation

zpool status
zfs list
zfs get all

mount after reboot

zfs set mountpoint=/export/db2 db2 

when you put in a new disk

fdisk -l 

to see what is new

sudo zpool create -f /srv/db3 raidz2 /dev/sdaa  /dev/sdab  /dev/sdac  /dev/sdad  /dev/sdae  /dev/sdaf  /dev/sdag  /dev/sdah  /dev/sdai  /dev/sdaj  /dev/sdak  /dev/sdal  
sudo zpool add -f /srv/db3 raidz2  /dev/sdam  /dev/sdan  /dev/sdao  /dev/sdap  /dev/sdaq  /dev/sdar  /dev/sdas  /dev/sdat  /dev/sdau  /dev/sdav  /dev/sdaw  /dev/sdax
zfs unmount db3
zfs mount db3

latest

zpool create -f db3 raidz2  /dev/sdy /dev/sdz  /dev/sdaa  /dev/sdab  /dev/sdac  /dev/sdad  /dev/sdae  /dev/sdaf  /dev/sdag  /dev/sdah  /dev/sdai  /dev/sdaj
zpool add -f db3 raidz2 /dev/sdak  /dev/sdal  /dev/sdam  /dev/sdan  /dev/sdao  /dev/sdap  /dev/sdaq  /dev/sdar  /dev/sdas  /dev/sdat  /dev/sdau  /dev/sdav
zpool create -f db4 raidz2 /dev/sdax /dev/sday /dev/sdaz /dev/sdba  /dev/sdbb  /dev/sdbc  /dev/sdbd  /dev/sdbe  /dev/sdbf  /dev/sdbg  /dev/sdbh  /dev/sdbi 
zpool add -f db4 raidz2 /dev/sdbj /dev/sdbk /dev/sdbl /dev/sdbm /dev/sdbn /dev/sdbo /dev/sdbp /dev/sdbq /dev/sdbr /dev/sdbs /dev/sdbt /dev/sdbu


Fri Jan 19 2018

zpool create -f db5 raidz2 /dev/sdbw /dev/sdbx /dev/sdby /dev/sdbz /dev/sdca  /dev/sdcb  /dev/sdcc  /dev/sdcd  /dev/sdce  /dev/sdcf  /dev/sdcg  /dev/sdch
zpool add -f db5 raidz2 /dev/sdci /dev/sdcj /dev/sdck /dev/sdcl /dev/sdcm /dev/sdcn /dev/sdco /dev/sdcp /dev/sdcq /dev/sdcr /dev/sdcs /dev/sdct
zfs mount db5

Wed Jan 24 2018

On tsadi

zpool create -f ex1 mirror /dev/sdaa /dev/sdab /dev/sdac /dev/sdad /dev/sdae
zpool add -f ex1 mirror /dev/sdaf /dev/sdag /dev/sdah /dev/sdai /dev/sdaj
zpool create -f ex2 mirror /dev/sdf /dev/sdg /dev/sdh /dev/sdi /dev/sdj
zpool add -f ex2 /dev/sdk /dev/sdl /dev/sdm /dev/sdn /dev/sdo
zpool create -f ex3 mirror /dev/sdp /dev/sdq /dev/sdr /dev/sds /dev/sdt
zpool add -f ex3 mirror /dev/sdu /dev/sdv /dev/sdw /dev/sdx /dev/sdy
zpool create -f ex4 mirror /dev/sdz /dev/sdak /dev/sdal
zpool add -f ex4 mirror /dev/sdam /dev/sdan /dev/sdao

On tsadi

zpool create -f ex1 mirror /dev/sdaa /dev/sdab mirror /dev/sdac /dev/sdad mirror /dev/sdae /dev/sdaf mirror /dev/sdag /dev/sdah mirror  /dev/sdai /dev/sdaj
zpool create -f ex2 mirror  /dev/sdf /dev/sdg mirror /dev/sdh /dev/sdi mirror /dev/sdj /dev/sdk mirror /dev/sdl /dev/sdm mirror /dev/sdn /dev/sdo
zpool create -f ex3 mirror /dev/sdp /dev/sdq mirror /dev/sdr /dev/sds mirro /dev/sdt /dev/sdu mirror /dev/sdv /dev/sdw mirror /dev/sdx /dev/sdy
zpool create -f ex4 mirror /dev/sdz /dev/sdak /dev/sdal  mirror /dev/sdam mirror /dev/sdan /dev/sdao

On lamed

zpool create -f ex5 mirror /dev/sdaa /dev/sdab mirror /dev/sdac /dev/sdad mirror /dev/sdae /dev/sdaf mirror /dev/sdag /dev/sdah mirror  /dev/sdai /dev/sdaj
zpool create -f ex6 mirror  /dev/sda /dev/sdb mirror /dev/sdc /dev/sdd mirror /dev/sde /dev/sdf mirror /dev/sdg /dev/sdh mirror /dev/sdi /dev/sdj
zpool create -f ex7 mirror  /dev/sdk /dev/sdl mirror /dev/sdm /dev/sdn mirror /dev/sdo /dev/sdp mirror /dev/sdq /dev/sdr mirror /dev/sds /dev/sdt
zpool create -f ex8 mirror /dev/sdu /dev/sdv mirror /dev/sdw /dev/sdx mirror /dev/sdy /dev/sdz


Sun Jan 19 2020

on mem2, sql system, note sda and sdc are system disks

zpool create -f sql1 raidz2  /dev/sdb /dev/sdc /dev/sde /dev/sdf /dev/sdg /dev/sdh /dev/sdi /dev/sdj /dev/sdk /dev/sdl /dev/sdm
zpool add     -f sql1 raidz2  /dev/sdn /dev/sdo /dev/sdp /dev/sdq /dev/sdr /dev/sds /dev/sdt /dev/sdu /dev/sdv /dev/sdw /dev/sdx

transform db4 on n-1-136 from z2 to z0 (or z1?)

zpool destroy db4
zpool create -f db4 raidz0 /dev/sdax /dev/sday /dev/sdaz /dev/sdba  /dev/sdbb  /dev/sdbc  /dev/sdbd  /dev/sdbe  /dev/sdbf  /dev/sdbg  /dev/sdbh  /dev/sdbi 
zpool add -f db4 raidz0 /dev/sdbj /dev/sdbk /dev/sdbl /dev/sdbm /dev/sdbn /dev/sdbo /dev/sdbp /dev/sdbq /dev/sdbr /dev/sdbs /dev/sdbt /dev/sdbu

zfs mount

recovery from accidental pool destruction

umount /mnt /mnt2
mdadm -S /dev/md125/dev/md126/dev/md127
sfdisk -d /dev/sda < sda.sfdisk
sfdisk -d /dev/sdb < sdb.sfdisk
sfdisk /dev/sda < sdb.sfdisk
mdadm --detail /dev/md127
mdadm -A -R /dev/md127/dev/sdb2/dev/sda2
mdadm /dev/md127 -a /dev/sda2
mdadm --detail /dev/md127
echo check > /sys/block/md127/md/sync_action
cat /proc/mdstat
mdadm --detail /dev/md126
mdadm -A -R /dev/md126/dev/sdb3/dev/sda3
mdadm /dev/md126 -a /dev/sda3
mdadm --detail /dev/md126
echo check > /sys/block/md126/md/sync_action
cat /proc/mdstat

Also switched the bios to boot from hd2 instead of hd1 (or something)

  • Recreate zpool with correct drives
  • Point an instance photorec at each of the wiped drives set to recover files of the following types: .gz, .solv (custom definition)


NOTE: If you destroyed your zpool with command 'zpool destroy', you can use the command 'zpool import' to view destroyed pools and recover the pool by doing 'zpool import <zpool name>'.

Example: Fixing degraded pool, replacing faulted disk

On Feb 22, 2019, one of nfs-ex9's disks became faulty.

-bash-4.2$ zpool status
pool: ex9
state: DEGRADED
status: One or more devices are faulted in response to persistent errors.
	Sufficient replicas exist for the pool to continue functioning in a
	degraded state.
action: Replace the faulted device, or use 'zpool clear' to mark the device
	repaired.
  scan: scrub canceled on Fri Feb 22 11:31:25 2019
config:
         raidz2-5                                      DEGRADED     0     0     0
sdae                                        ONLINE       0     0     0
sdaf                                        ONLINE       0     0     0
sdag                                        ONLINE       0     0     0
sdah                                        FAULTED     18     0     0  too many errors
sdai                                        ONLINE       0     0     0
sdaj                                        ONLINE       0     0     0


I did the following:

-bash-4.2$ sudo zpool offline ex9 sdb

Then I went to the server room to see that disk 1 still had a red light due to the fault. I pulled the disk out. Inserted a fresh one of the same brand, a Seagate Exos X12. The server detected the new disk and set the disk name as /dev/sdb, just like the one I just pulled out. Finally, I did the following command.

-bash-4.2$ sudo zpool replace ex9 /dev/sdah
-bash-4.2$ zpool status
 pool: ex9
state: DEGRADED
status: One or more devices is currently being resilvered.  The pool will
continue to function, possibly in a degraded state.
action: Wait for the resilver to complete.
 scan: resilver in progress since Tue Mar 19 14:06:33 2019
1.37G scanned out of 51.8T at 127M/s, 118h33m to go
37.9M resilvered, 0.00% done
.
.
.
	  raidz2-5                                      DEGRADED     0     0     0
   sdae                                        ONLINE       0     0     0
   sdaf                                        ONLINE       0     0     0
   sdag                                        ONLINE       0     0     0
   replacing-3                                 DEGRADED     0     0     0
     old                                       FAULTED     18     0     0  too many errors
     sdah                                      ONLINE       0     0     0  (resilvering)
   sdai                                        ONLINE       0     0     0
   sdaj                                        ONLINE       0     0     0

Resilvering is the process of a disk being rebuilt from its parity group. Once it is finished, you should be good to go again.

For qof/nfs-ex9, we had an issue with the disk LED for /dev/sdah still showing up red despite the resilvering occurring. To return the disk LED to a normal status, issue the following command:

$ sudo ledctl normal=/dev/<disk id>
Example: $ sudo ledctl normal=/dev/sdah