FreeNas: Diskfailure – ZFS has attempted to repair the affected data.

Z.B. nach einem Stromausfall oder einer defekten Disk, etc.:

Run ‹zpool status -x› to determine which pool has experienced errors:

Find the device with a non-zero error count for READ, WRITE, or CKSUM. This indicates that the device has experienced a read I/O error, write I/O error, or checksum validation error. Because the device is part of a mirror or RAID-Z device, ZFS was able to recover from the error and subsequently repair the damaged data.

If these errors persist over a period of time, ZFS may determine the device is faulty and mark it as such. However, these error counts may or may not indicate that the device is unusable. It depends on how the errors were caused, which the administrator can determine in advance of any ZFS diagnosis. For example, the following cases will all produce errors that do not indicate potential device failure:

  • A network attached device lost connectivity but has now recovered
  • A device suffered from a bit flip, an expected event over long periods of time
  • An administrator accidentally wrote over a portion of the disk using another program

In these cases, the presence of errors does not indicate that the device is likely to fail in the future, and therefore does not need to be replaced. If this is the case, then the device errors should be cleared using ‹zpool clear›:

On the other hand, errors may very well indicate that the device has failed or is about to fail. If there are continual I/O errors to a device that is otherwise attached and functioning on the system, it most likely needs to be replaced. The administrator should check the system log for any driver messages that may indicate hardware failure. If it is determined that the device needs to be replaced, then the ‹zpool replace› command should be used:

This will attach the new device to the pool and begin resilvering data to it. Once the resilvering process is complete, the old device will automatically be removed from the pool, at which point it can safely be removed from the system. If the device needs to be replaced in-place (because there are no available spare devices), the original device can be removed and replaced with a new device, at which point a different form of ‹zpool replace› can be used:

This assumes that the original device at ‹c0t0d0› has been replaced with a new device under the same path, and will be replaced appropriately.

You can monitor the progress of the resilvering operation by using the ‹zpool status -x› command:

25. September 2015 3830 webadmin  General
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