Solaris ZFS Administration Guide

Determining the Type of Device Failure

The term damaged device is rather vague, and can describe a number of possible situations:

Determining exactly what is wrong can be a difficult process. The first step is to examine the error counts in the zpool status output as follows:

# zpool status -v pool

The errors are divided into I/O errors and checksum errors, both of which might indicate the possible failure type. Typical operation predicts a very small number of errors (just a few over long periods of time). If you are seeing large numbers of errors, then this situation probably indicates impending or complete device failure. However, the pathology for administrator error can result in large error counts. The other source of information is the system log. If the log shows a large number of SCSI or fibre channel driver messages, then this situation probably indicates serious hardware problems. If no syslog messages are generated, then the damage is likely transient.

The goal is to answer the following question:

Is another error likely to occur on this device?

Errors that happen only once are considered transient, and do not indicate potential failure. Errors that are persistent or severe enough to indicate potential hardware failure are considered “fatal.” The act of determining the type of error is beyond the scope of any automated software currently available with ZFS, and so much must be done manually by you, the administrator. Once the determination is made, the appropriate action can be taken. Either clear the transient errors or replace the device due to fatal errors. These repair procedures are described in the next sections.

Even if the device errors are considered transient, it still may have caused uncorrectable data errors within the pool. These errors require special repair procedures, even if the underlying device is deemed healthy or otherwise repaired. For more information on repairing data errors, see Repairing Damaged Data.