The config field in the zpool status output describes the configuration of the devices in the pool, as well as their state and any errors generated from the devices. The state can be one of the following: ONLINE, FAULTED, DEGRADED, UNAVAIL, or OFFLINE. If the state is anything but ONLINE, the fault tolerance of the pool has been compromised.
The second section of the configuration output displays error statistics. These errors are divided into three categories:
READ – I/O errors that occurred while issuing a read request
WRITE – I/O errors that occurred while issuing a write request
CKSUM – Checksum errors, meaning that the device returned corrupted data as the result of a read request
These errors can be used to determine if the damage is permanent. A small number of I/O errors might indicate a temporary outage, while a large number might indicate a permanent problem with the device. These errors do not necessarily correspond to data corruption as interpreted by applications. If the device is in a redundant configuration, the devices might show uncorrectable errors, while no errors appear at the mirror or RAID-Z device level. In such cases, ZFS successfully retrieved the good data and attempted to heal the damaged data from existing replicas.
For more information about interpreting these errors, see Determining the Type of Device Failure.
Finally, additional auxiliary information is displayed in the last column of the zpool status output. This information expands on the state field, aiding in the diagnosis of failures. If a device is FAULTED, this field indicates whether the device is inaccessible or whether the data on the device is corrupted. If the device is undergoing resilvering, this field displays the current progress.
For information about monitoring resilvering progress, see Viewing Resilvering Status.