I’ve bought six years ago, in April 2008, a Sun Ultra 20 M2 Workstation, Dual-Core 2.6 GHz AMD Opteron Processor – Model 1218. The server contains four hard drives of 250Go and I installed the now abandoned operating system OpenSolaris. On top of that, I used software RAID and virtual storage pools offered by ZFS. The choice for that was mainly because this server doesn’t have any hardware RAID card. Anyway, after so many years of good and loyal service, one of the four hard drives died and I had to replace it. 🙁

First of all, let’s have a look on how I configured the pools:

smoreau@Sun-Server:~# zpool status
  pool: dpool
 state: DEGRADED
status: One or more devices could not be opened.  Sufficient replicas exist for
        the pool to continue functioning in a degraded state.
action: Attach the missing device and online it using 'zpool online'.
   see: http://www.sun.com/msg/ZFS-8000-2Q
 scrub: scrub completed after 0h20m with 0 errors on Sat May 18 15:45:00 2013
config:

        NAME          STATE     READ WRITE CKSUM
        dpool         DEGRADED     0     0     0
          raidz1      DEGRADED     0     0     0
            c3t1d0s4  ONLINE       0     0     0
            c3t2d0s4  ONLINE       0     0     0
            c3t3d0s4  UNAVAIL      0 11.8K     0  cannot open
            c3t4d0s4  ONLINE       0     0     0

errors: No known data errors

  pool: rpool
 state: ONLINE
 scrub: none requested
config:

        NAME          STATE     READ WRITE CKSUM
        rpool         ONLINE       0     0     0
          mirror      ONLINE       0     0     0
            c3t1d0s0  ONLINE       0     0     0
            c3t2d0s0  ONLINE       0     0     0
        spares
          c3t3d0s0    UNAVAIL   cannot open
          c3t4d0s0    AVAIL   

errors: No known data errors

As you can see, I configured two pools:

1. A raid pool called ‘dpool’ using the four drives
2. A mirror pool called ‘rpool’ using two drives and having two spares

You can also see above that one of the disks (c3t3d0) doesn’t seem to work any longer. This is the faulty disk which needs to be replaced.
Please note that it was the first time I had to replace a disk in this server. So, you will notice that I struggled a little bit to find the right way. 😉

The first thing I did was shutting down the machine and replacing the physical disk. Once I’ve done that, I simply reboot the machine.
Let’s now check if the drive has been recognised by the system:

smoreau@Sun-Server:~# cfgadm -alv | grep c3t3d0
sata4/3::dsk/c3t3d0            connected    configured   ok         Mod: SEAGATE ST32500NSSUN250G 0814B5MKCY FRev: 3AZQ SN: 5QE5MKCY

So far so good, the drive has been successfully connected and configured. 🙂

I then try a few things to add the new drive in the pools:

smoreau@Sun-Server:~# zpool online dpool c3t3d0s4
warning: device 'c3t3d0s4' onlined, but remains in faulted state
use 'zpool replace' to replace devices that are no longer present

As suggested in the error message, I tried the following:

smoreau@Sun-Server:~# zpool replace dpool c3t3d0s4
cannot open '/dev/dsk/c3t3d0s4': I/O error

Looking at this error on the internet, I found the following explanation on the ZFS Troubleshooting Guide:

This error means that the disk slice doesn’t have any disk space allocated to it or possibly that a Solaris fdisk partition and the slice doesn’t exist on an x86 system. Use the format utility to allocate disk space to a slice. If the x86 system doesn’t have a Solaris fdisk partition, use the fdisk utility to create one.

This is pretty clear, I installed the new drive but I didn’t partition it.
Let’s do it then.

First of all, let’s check the partition table on one of the healthy drive using the command format -e c3t4d0:

partition> print
Current partition table (original):
Total disk cylinders available: 30398 + 2 (reserved cylinders)

Part      Tag    Flag     Cylinders         Size            Blocks
  0       root    wm       1 -  4289       32.86GB    (4289/0/0)   68902785
  1 unassigned    wm       0                0         (0/0/0)             0
  2     backup    wu       0 - 30397      232.86GB    (30398/0/0) 488343870
  3 unassigned    wm       0                0         (0/0/0)             0
  4 unassigned    wm    4290 - 30396      199.99GB    (26107/0/0) 419408955
  5 unassigned    wm       0                0         (0/0/0)             0
  6 unassigned    wm       0                0         (0/0/0)             0
  7 unassigned    wm       0                0         (0/0/0)             0
  8       boot    wu       0 -     0        7.84MB    (1/0/0)         16065
  9 unassigned    wm       0                0         (0/0/0)             0

Using the table below and the article Mirroring my Solaris OS partition, I manually recreated the partition table on the new drive.

Once I’ve done it, I ran the following commands:

smoreau@Sun-Server:~# zpool replace dpool c3t3d0s4
invalid vdev specification
use '-f' to override the following errors:
/dev/dsk/c3t3d0s4 overlaps with /dev/dsk/c3t3d0s2

smoreau@Sun-Server:~# zpool replace -f dpool c3t3d0s4

smoreau@Sun-Server:~# zpool status dpool
  pool: dpool
 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.
 scrub: resilver in progress for 0h0m, 0.03% done, 13h27m to go
config:

        NAME                STATE     READ WRITE CKSUM
        dpool               DEGRADED     0     0     0
          raidz1            DEGRADED     0     0     0
            c3t1d0s4        ONLINE       0     0     0  2.34M resilvered
            c3t2d0s4        ONLINE       0     0     0  2.34M resilvered
            replacing       DEGRADED     0     0     0
              c3t3d0s4/old  FAULTED      0 8.04K     0  corrupted data
              c3t3d0s4      ONLINE       0     0     0  3.50M resilvered
            c3t4d0s4        ONLINE       0     0     0  2.23M resilvered

errors: No known data errors

This seems to be working, we can see below that the system is rebuilding the data on the new drive.

After a few minutes, we can see that the pool is healthy again:

smoreau@Sun-Server:~# zpool status dpool
  pool: dpool
 state: ONLINE
 scrub: resilver completed after 0h24m with 0 errors on Sat May 18 16:50:44 2013
config:

        NAME          STATE     READ WRITE CKSUM
        dpool         ONLINE       0     0     0
          raidz1      ONLINE       0     0     0
            c3t1d0s4  ONLINE       0     0     0  43.8M resilvered
            c3t2d0s4  ONLINE       0     0     0  43.8M resilvered
            c3t3d0s4  ONLINE       0     0     0  11.8G resilvered
            c3t4d0s4  ONLINE       0     0     0  36.1M resilvered

errors: No known data errors