Veritas NetBackup™ Administrator's Guide, Volume II
- NetBackup licensing models and the nbdeployutil utility
- How capacity licensing works
- Creating and viewing the licensing report
- Reviewing a capacity licensing report
- Reconciling the capacity licensing report results
- Reviewing a traditional licensing report
- Reviewing an NEVC licensing report
- Additional configuration
- About dynamic host name and IP addressing
- About busy file processing on UNIX clients
- About the Shared Storage Option
- DELETE About configuring the Shared Storage Option in NetBackup
- Viewing SSO summary reports
- About the vm.conf configuration file
- Holds Management
- Menu user interfaces on UNIX
- About the tpconfig device configuration utility
- About the NetBackup Disk Configuration Utility
- Reference topics
- Host name rules
- About reading backup images with nbtar or tar32.exe
- Factors that affect backup time
- NetBackup notify scripts
- Media and device management best practices
- About TapeAlert
- About tape drive cleaning
- How NetBackup reserves drives
- About SCSI persistent reserve
- About the SPC-2 SCSI reserve process
- About checking for data loss
- About checking for tape and driver configuration errors
- How NetBackup selects media
- About selecting media in robots
- About selecting media in standalone drives
- About Tape I/O commands on UNIX
About SCSI persistent reserve
The NetBackup process that reads from or writes to the media in a drive (bptm) issues SCSI persistent reserve commands to do the following:
Register with the tape drive's device server (the server is a logical unit within a drive that processes SCSI tasks)
Request an exclusive access reservation
If the tape drive's device server grants the reservation, the NetBackup process has exclusive use of the device. The reservation prevents other host bus adapters (HBAs) from issuing any commands that can cause data loss.
If the reservation fails, NetBackup fails the job.
When the NetBackup process is finished with the drive, NetBackup unloads the drive and sends a persistent reserve clear command to the drive. The command removes both the reservation and the registration.
SCSI persistent reserve also provides device status detection, which NetBackup uses to resolve reservation conflicts within NetBackup.
The reservation does not prevent other applications on the host that has the reservation from using the same device and from causing data loss. For example, if a user on the same host issues a UNIX mt command, the mt command can take control of the drive.
Also, other HBAs can clear or release a SCSI persistent reservation. Therefore, an application can clear another HBA reservation (although it should not do so).