ZFS install (Notes)

Very terse notes...

• ZFS linux implementation: http://zfsonlinux.org/
• Installation Centos : http://zfsonlinux.org/epel.html
• ZFS docs : http://docs.oracle.com/cd/E19253-01/819-5461/index.html

#1 ZFS Install

CentOS Linux release 7.1.1503 (Core) (on VMWare Version 7.1.0)

Before installing you should run

$ yum upgrade

Then follow steps from http://zfsonlinux.org/epel.html

$ sudo yum localinstall --nogpgcheck https://download.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-5.noarch.rpm
$ sudo yum localinstall --nogpgcheck http://archive.zfsonlinux.org/epel/zfs-release.el7.noarch.rpm
$ sudo yum install kernel-devel zfs

After installation try with :

$ zpool list 

If you get following error :

Failed to load ZFS module stack.
Load the module manually by running 'insmod /zfs.ko' as root.

$ cat /proc/filesystems
...
nodev   hugetlbfs
nodev   autofs
nodev   pstore
nodev   mqueue
nodev   selinuxfs
xfs
nodev   zfs

$ lsmod | grep zfs
zfs 2236101 4
zunicode 331170 1 zfs
zavl 14933 1 zfs
zcommon 51315 1 zfs
znvpair 89086 2 zfs,zcommon
spl 91752 3 zfs,zcommon,znvpair

#2 Test (crate pool)

Using VMWare crete 3 disks for tests pupose (just 1G of space).
Use shell to determine all available/attached hard disks on the linux box :

$ lsblk -io KNAME,TYPE,SIZE,MODEL
 KNAME TYPE  SIZE MODEL
 sda   disk   20G VMware Virtual S
 sda1  part  500M
 sda2  part 19.5G
 dm-0  lvm  17.5G
 dm-1  lvm     2G
 sdb   disk    1G VMware Virtual S
 sdc   disk    1G VMware Virtual S
 sdd   disk    1G VMware Virtual S
 sr0   rom  66.6M VMware IDE CDR10

Now create a new pool :

$ zpool create tank mirror sdb sdc
invalid vdev specification
use '-f' to override the following errors:
/dev/sdb does not contain an EFI label but it may contain partition 
information in the MBR.

You have to create GPT on sdb and sdc :

$ fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0xe3225926.

Command (m for help): g
Building a new GPT disklabel (GUID: 4993FDA1-5E3D-4A4D-91CB-77BD0C85BD98)

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

(please do the same on /dev/sdc)

Again create a new pool  :

$ zpool create tank mirror sdb sdc
$ zpool list
 NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
 tank 1008M 56.5K 1008M - 0% 0% 1.00x ONLINE -
$ mount
 proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
 sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime,seclabel)
 ...
 tank on /tank type zfs (rw,relatime,seclabel,xattr,noacl)

#3 Simulate disk crash (sbd)

Remove from VMWare a disk (for example /dev/sdb) which was part of pool created above (we are simulating that sdb is broken). 

After you used VMWare panel in order to remove sdb (please note that sbd will be moved by VMWare as the new sdb) execute :

$ zpool status tanks
cannot open 'tank': no such pool

$ zpool import
    pool: tank
    id: 17334258515364360988
    state: DEGRADED
    status: One or more devices contains corrupted data.
    action: The pool can be imported despite missing or damaged devices.  The
       fault tolerance of the pool may be compromised if imported.
       see: http://zfsonlinux.org/msg/ZFS-8000-4J
    config:
     tank        DEGRADED
     mirror-0    DEGRADED
         sdb     UNAVAIL
         sdc     ONLINE

tank can be imported but as degradated (sdb is unavaiable)... so import tank also if pool is in state DEGRADED :

$ zpool import tank
$ zpool status
  pool: tank
  state: DEGRADED
  status: One or more devices could not be used because the label is missing or
    invalid.  Sufficient replicas exist for the pool to continue
    functioning in a degraded state.
    action: Replace the device using 'zpool replace'.
    see: http://zfsonlinux.org/msg/ZFS-8000-4J
  scan: none requested
  config:
    NAME                               STATE     READ WRITE CKSUM
    tank                               DEGRADED     0     0     0
      mirror-0                         DEGRADED     0     0     0
        12026337132713439253           FAULTED      0     0     0  was /dev/sdb1
        pci-0000:00:10.0-scsi-0:0:2:0  ONLINE       0     0     0
errors: No known data errors

Replace broken disk with hot spare : zpool replace tank 

$ zpool replace tank sdb sdc

Note : removing the old_sdc (from VMWare) the disk sdd is now changed to a new location as sdc