System Reporting of ZFS Error Messages

In addition to persistently keeping track of errors within the pool, ZFS also displays syslog messages when events of interest occur. The following scenarios generate events to notify the administrator:

• Device state transition – If a device becomes FAULTED, ZFS logs a message indicating that the fault tolerance of the pool might be compromised. A similar message is sent if the device is later brought online, restoring the pool to health.

• Data corruption – If any data corruption is detected, ZFS logs a message describing when and where the corruption was detected. This message is only logged the first time it is detected. Subsequent accesses do not generate a message.

• Pool failures and device failures – If a pool failure or device failure occurs, the fault manager daemon reports these errors through syslog messages as well as the fmdump command.

If ZFS detects a device error and automatically recovers from it, no notification occurs. Such errors do not constitute a failure in the pool redundancy or data integrity. Moreover, such errors are typically the result of a driver problem accompanied by its own set of error messages.