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SAF-TE, abbreviated for SCSI Accessed Fault Tolerant Enclosure, 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, auto-rebuild of RAID array is performed automatically after replacing a failed drive. This is a very convenience feature since system administrators do not have to start the process manually. Without SAF-TE, auto-rebuild of RAID array can only occur if spare disk is presented. Using SAF-TE, users can maximize the size of the disk array since spare disk is not required. Other features of SAF-TE include:
SAF-TE enables the system administrator to identify the correct failed drive through the flashing LED on the drive carrier. This feature is very important for storage server running with large number of hard drives off 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 enclosure(s) in real time. This allows system administrator 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.
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