Recommended use for Enable SCSI reserve property
All tape drive and bridge vendors support the SPC-2 SCSI reserve and release method. NetBackup has used SPC-2 SCSI reserve since NetBackup 3.4.3, and it is the default tape drive reservation method in NetBackup. SPC-2 SCSI reserve is effective for most NetBackup environments.
The SCSI persistent reserve method provides device status and correction and may be more effective in the following environments:
Where NetBackup media servers operate in a cluster environment.
NetBackup can recover and use a reserved drive after a failover (if NetBackup owns the reservation). (With SPC-2 SCSI reserve, the drive must usually be reset because the reservation owner is inoperative.)
Where the drive has high availability.
NetBackup can resolve NetBackup drive reservation conflicts and maintain high drive availability. (SPC-2 SCSI reserve provides no method for drive status detection.)
However, the SCSI persistent reserve method is not supported or not supported correctly by all device vendors. Therefore, thoroughly analyze the environment to ensure that all of the hardware supports SCSI persistent reserve correctly.
Veritas recommends careful consideration of all of the following factors before is used:
Only a limited number of tape drive vendors support SCSI persistent reserve.
SCSI persistent reserve is not supported or not supported correctly by all Fibre Channel bridge vendors. Incorrect support in a bridge means no access protection. Therefore, if the environment uses bridges, do not use SCSI persistent reserve.
If parallel SCSI buses are used, carefully consider the use of SCSI persistent reserve. Usually, parallel drives are not shared, so SCSI persistent reserve protection is not required. Also, parallel drives are usually on a bridge, and bridges do not support SCSI persistent reserve correctly. Therefore, if the environment uses parallel SCSI buses, do not use SCSI persistent reserve.
The operating system tape drivers may require extensive configuration to use SCSI persistent reserve. For example, if the tape drives do not support SPC-3 Compatible Reservation Handling (CRH), ensure that the operating system does not issue SPC-2 reserve and release commands.
If any of the hardware does not support SCSI persistent reserve, Veritas recommends that SCSI persistent reserve is not used.