Spare Disks
A SANnet II 200 SCSI array disk can be assigned as a data disk or a spare disk. When configured as a spare, it can serve as a local spare to one specified logical drive or as a global spare available to all logical drives. More than one spare disk can exist for a particular logical drive and even combinations of local and global disks. It is a good practice to ensure every logical drive is protected by at least one spare disk, even if many logical drives are sharing spare disks.
Logical Drive Rebuilding
Spare disks are destined to become part of a logical drive rebuilding process. SANnet II 200 SCSI arrays provide several options for detecting the need to rebuild a logical drive. For example, an array may wait until a disk fails completely before rebuilding a logical drive or detect a malfunctioning disk and rebuild the logical drive before the disk fails completely. Several options exist for choosing logical drive rebuilding preferences.
When a disk fails without warning, the controller first examines whether there is a local spare disk assigned to this logical drive. If yes, it automatically starts to rebuild the data of the failed disk to it. If there is no local spare available, the controller next searches for a global spare to rebuild the logical drive. If no valid spare disks are available, the logical drive rebuilding waits until a spare disk becomes available, generally after the replacement of the failed disk.
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