Summary
This article describes how to configure an enterprise where the tape SAN paths are accessible through both DPX device servers and a NetApp Filer.
Symptoms
If the steps described in this article are not followed, the SCSI reservation attempt on the NetApp SAN paths will fail when running jobs.
Resolution
This solution is supported for OnTap versions 7.1.1 and newer. OnTap versions lower than 7.1.1 will not work properly with Backup Express SCSI reserve/release requests. It is recommended that customers upgrade to the latest version of OnTap to take advantage of new updates available from Network Appliance.
Note: If you have an older version of OnTap, it may not be appropriate for you to upgrade directly to the latest version. Some versions of OnTap require that you first upgrade to an interim version before upgrading to the latest release. Please contact your NetApp reseller or NetApp technical support center for additional information on upgrades.
The general solution to supporting SCSI reserve/release on shared SAN networks is to enable SCSI reserve/release on all DPX device servers (default setting), turn it off in the Backup Express enterprise for each NetApp that acts as a SAN path, and then enable reserve/release on your Filer via OnTap command line options setting.
Step 1: Disable reservations for Filers in DPX enterprise
To do this, go to Configure > Enterprise, find the Filer in question, right-click on the node and choose SCSI reserve/release.
This opens a dialog box titled Define Device Reserve/Release Option. Make sure the option is set to No and click OK:
Turning this off in Backup Express will prevent DPX from attempting to handle the SCSI reserve/release directly.
Step 2: Enable reservations via OnTap on each Filer
Once the SCSI reserve/release has been disabled in the Enterprise, you will need to enable it through the OnTap command line interface. You will need to set the tape.reservations option to scsi. The following OnTap command will accomplish this:
options tape.reservations scsi
Verify that this setting is in place with:
options tape
And you will see output similar to the following:
FilerR200*> options tape
tape.reservations scsi
Final Notes:
Once these steps are complete, DPX will manage SCSI reserve/release directly with its device servers, and OnTap will manage reservations on its own. Since each path has a way to manage reservations, tape conflicts will not occur. SCSI conflicts will occur when devices on the SAN do not properly request reservations; thus, when enabling any device such as a filer to manage itself, care must be taken to check that new system settings take place, and are consistent for all possible paths.
The easiest way to check if a Filer is properly setting reservations to execute a test similar to the following:
1) Run a backup job that uses a SAN path through your filer. This could be by either
- Choosing a drive that only has Filer SAN paths defined, or
- Running an NDMP backup of a Filer volume (this would cause DPX to use/prefer a local SAN tape path on the Filer).
Wait for a tape to mount and data transfer to begin.
2) Log into another DPX device server and attempt to execute tape commands (such as Backup Express 'tapedump') on the same SAN attached tape drive.
If The Filer is properly setting SCSI reserve/release, access to the SAN tape device in step #2 above will fail and the backup job started in step #1 should complete. For an extra level of testing, restore some data from the completed backup.