SAF-TE
SCSI Accessed Fault Tolerant Enclosure (SAF-TE), is the method by which SCSI-based storage devices, controllers, back planes, power supplies, and other components communicate their status to monitoring applications. Environmental monitoring, such as storage chassis temperature and fan speed, can also be tracked through SAF-TE. Messaging from enclosures that are compliant with SAF-TE standards can be translated to audible and visible notifications on the JBOD system itself - status lights and alarms - to indicate failure of critical system components.
When a SCSI back plane includes the SAF-TE controller, rebuilding of the RAID array is performed automatically after replacing a failed drive. This is a very convenient feature since system administrators do not have to start the process manually. Without SAF-TE, auto-rebuild of RAID arrays can only occur if a spare disk is present. Using SAF-TE, users can maximize the size of the disk array since spare disks are not required. Other features of SAF-TE include:
- SAF-TE enables the system administrator to identify the correct failed drive through a flashing LED on the drive carrier. This feature is very important for storage servers running with large numbers of hard drives connected to multiple controllers.
- During the rebuild process, the status LED on the pertinent drive bay flashes continuously. This visual display indicates that the disk array is being rebuilt.
- When a disk fails, the SAF-TE controller immediately informs the host chassis. At such time, the chassis generates audible beeps to alert the users about the critical condition.
- SAF-TE reports critical changes in the system environment occurring on the external disk enclosures in real time. This allows system administrators to take the appropriate action quickly. An example of critical changes is loss of power on the redundant power supply or failure on the chassis fan(s).
SAF-TE is included as a standard feature in all ASL servers that support hotswap SCSI drives.