Veritas NetBackup™ Administrator's Guide, Volume II
- NetBackup licensing models and the nbdeployutil utility
- Additional configuration
- About dynamic host name and IP addressing
- About busy file processing on UNIX clients
- About the Shared Storage Option
- 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 Tape I/O commands on UNIX
About SPC-2 SCSI reserve commands
When a device receives an exclusive access type SCSI persistent reservation command, it does not process commands from any other HBA. The device processes commands from another HBA only when the HBA that owns the reservation issues the release command. If an application sends a command to a reserved device, the device fails the command by returning a status of RESERVATION CONFLICT. The only exceptions to this action are several commands that cannot interfere with the reservation, such as Inquiry or Request Sense.
A device stays reserved until one of the following events occurs on the device:
Released by the HBA that reserved it
Released by a TARGET or a LOGICAL UNIT RESET
These resets are protocol-dependent and differ between parallel SCSI and FCP (SCSI on Fibre Channel ). These resets can be issued from any HBA.
Released by Fibre Channel LOGO, PLOGO, PRLI, PRLO, or TPRLO action or failed discovery (link actions)
Power cycled
A negative consequence of SPC-2 SCSI reserve occurs if the HBA that owns the reservation fails. A device stays reserved until the reservation is removed or broken. Only the original HBA can remove the reservation, which means the system must be available. If the HBA that owns the reservation fails, it cannot remove the reservation. Therefore, the reservation must be broken.
To break a reservation, one of the following actions must break the reservation:
SCSI reset
Bus device reset
LUN device reset
Power cycle
Fibre Channel link actions may break reservations
SPC-2 SCSI reserve commands are mandatory for all SCSI-2 and SCSI-3 devices. See the SCSI 2 standard for a detailed description of SCSI reserve command operation and behavior.