Managing ZFS File Systems in Oracle® Solaris 11.2

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Updated: December 2014

Resolving a Missing or Removed Device

If a device cannot be opened, it displays the UNAVAIL state in the zpool status output. This state means that ZFS was unable to open the device when the pool was first accessed, or the device has since become unavailable. If the device causes a top-level virtual device to be unavailable, then nothing in the pool can be accessed. Otherwise, the fault tolerance of the pool might be compromised. In either case, the device just needs to be reattached to the system to restore normal operations. If you need to replace a device that is UNAVAIL because it has failed, see Replacing a Device in a ZFS Storage Pool.

If a device is UNAVAIL in a root pool or a mirrored root pool, see the following references:

For example, you might see a message similar to the following from fmd after a device failure:

SUNW-MSG-ID: ZFS-8000-QJ, TYPE: Fault, VER: 1, SEVERITY: Minor
EVENT-TIME: Wed Jun 20 13:09:55 MDT 2012
SOURCE: zfs-diagnosis, REV: 1.0
EVENT-ID: e13312e0-be0a-439b-d7d3-cddaefe717b0
DESC: Outstanding dtls on ZFS device 'id1,sd@n5000c500335dc60f/a' in pool 'pond'.
AUTO-RESPONSE: No automated response will occur.
IMPACT: None at this time.
REC-ACTION: Use 'fmadm faulty' to provide a more detailed view of this event.
Run 'zpool status -lx' for more information. Please refer to the associated
reference document at for the latest
service procedures and policies regarding this diagnosis.

To view more detailed information about the device problem and the resolution, use the zpool status –v command. For example:

# zpool status -v
pool: pond
status: One or more devices are unavailable in response to persistent errors.
Sufficient replicas exist for the pool to continue functioning in a
degraded state.
action: Determine if the device needs to be replaced, and clear the errors
using 'zpool clear' or 'fmadm repaired', or replace the device
with 'zpool replace'.
scan: scrub repaired 0 in 0h0m with 0 errors on Wed Jun 20 13:16:09 2012

NAME                   STATE     READ WRITE CKSUM
pond                   DEGRADED     0     0     0
mirror-0               ONLINE       0     0     0
c0t5000C500335F95E3d0  ONLINE       0     0     0
c0t5000C500335F907Fd0  ONLINE       0     0     0
mirror-1               DEGRADED     0     0     0
c0t5000C500335BD117d0  ONLINE       0     0     0
c0t5000C500335DC60Fd0  UNAVAIL      0     0     0

device details:

c0t5000C500335DC60Fd0    UNAVAIL          cannot open
status: ZFS detected errors on this device.
The device was missing.
see: for recovery

You can see from this output that the c0t5000C500335DC60Fd0 device is not functioning. If you determine that the device is faulty, replace it.

If necessary, use the zpool online command to bring the replaced device online. For example:

# zpool online pond c0t5000C500335DC60Fd0

Let FMA know that the device has been replaced if the output of the fmadm faulty identifies the device error. For example:

# fmadm faulty
--------------- ------------------------------------  -------------- ---------
TIME            EVENT-ID                              MSG-ID         SEVERITY
--------------- ------------------------------------  -------------- ---------
Jun 20 13:15:41 3745f745-371c-c2d3-d940-93acbb881bd8  ZFS-8000-LR    Major

Problem Status    : solved
Diag Engine       : zfs-diagnosis / 1.0
Manufacturer  : unknown
Name          : ORCL,SPARC-T3-4
Part_Number   : unknown
Serial_Number : 1120BDRCCD
Host_ID       : 84a02d28

Suspect 1 of 1 :
Fault class : fault.fs.zfs.open_failed
Certainty   : 100%
Affects     : zfs://pool=86124fa573cad84e/
Status      : faulted and taken out of service

Name             : "zfs://pool=86124fa573cad84e/
Status        : faulty

Description : ZFS device 'id1,sd@n5000c500335dc60f/a' 
in pool 'pond' failed to open.

Response    : An attempt will be made to activate a hot spare if available.

Impact      : Fault tolerance of the pool may be compromised.

Action      : Use 'fmadm faulty' to provide a more detailed view of this event.
Run 'zpool status -lx' for more information. Please refer to the
associated reference document at for the latest service
procedures and policies regarding this diagnosis.

Extract the string in the Affects: section of the fmadm faulty output and include it with the following command to let FMA know that the device is replaced:

# fmadm repaired zfs://pool=86124fa573cad84e/ \
   vdev=25d36cd46e0a7f49/pool_name=pond/ \
fmadm: recorded repair to of zfs://pool=86124fa573cad84e/

As a last step, confirm that the pool with the replaced device is healthy. For example:

# zpool status -x tank
pool 'tank' is healthy

Resolving a Removed Device

If a device is completely removed from the system, ZFS detects that the device cannot be opened and places it in the REMOVED state. Depending on the data replication level of the pool, this removal might or might not result in the entire pool becoming unavailable. If one disk in a mirrored or RAID-Z device is removed, the pool continues to be accessible. A pool might become UNAVAIL, which means no data is accessible until the device is reattached, under the following conditions:

If a redundant storage pool device is accidentally removed and reinserted, then you can just clear the device error, in most cases. For example:

# zpool clear tank c1t1d0

Physically Reattaching a Device

Exactly how a missing device is reattached depends on the device in question. If the device is a network-attached drive, connectivity to the network should be restored. If the device is a USB device or other removable media, it should be reattached to the system. If the device is a local disk, a controller might have failed such that the device is no longer visible to the system. In this case, the controller should be replaced, at which point the disks will again be available. Other problems can exist and depend on the type of hardware and its configuration. If a drive fails and it is no longer visible to the system, the device should be treated as a damaged device. Follow the procedures in Replacing or Repairing a Damaged Device.

A pool might be SUSPENDED if device connectivity is compromised. A SUSPENDED pool remains in the wait state until the device issue is resolved. For example:

# zpool status cybermen
pool: cybermen
status: One or more devices are unavailable in response to IO failures.
The pool is suspended.
action: Make sure the affected devices are connected, then run 'zpool clear' or
'fmadm repaired'.
Run 'zpool status -v' to see device specific details.
scan: none requested

cybermen   UNAVAIL      0    16     0
c8t3d0     UNAVAIL      0     0     0
c8t1d0     UNAVAIL      0     0     0

After device connectivity is restored, clear the pool or device errors.

# zpool clear cybermen
# fmadm repaired zfs://pool=name/vdev=guid

Notifying ZFS of Device Availability

After a device is reattached to the system, ZFS might or might not automatically detect its availability. If the pool was previously UNAVAIL or SUSPENDED, or the system was rebooted as part of the attach procedure, then ZFS automatically rescans all devices when it tries to open the pool. If the pool was degraded and the device was replaced while the system was running, you must notify ZFS that the device is now available and ready to be reopened by using the zpool online command. For example:

# zpool online tank c0t1d0

For more information about bringing devices online, see Bringing a Device Online.