Summary
From the SAN device server, a tape drive is not visible using the 'detect -q' command. Once the tape drive reboots, it is accessible from the device server.
Symptoms
From the SAN device server, a tape drive is not visible using the 'detect -q' command. Once the tape drive reboots, it is accessible from the device server.
Brocade portCfgFillWord mode 3 causes tape drives to be offline from the SAN.
Starting with FOS v6.3.1a, Brocade added two new fillword modes. Mode 3 is the recommended mode for most 8 GB devices. However, mode 3 causes problems for tape drives operating in the loop topology at 8 GBPS.
Resolution
The issue was discovered while troubleshooting IBM LTO5 drives. IBM provided new firmware (LTO5_BBNE) to correct this issue as a workaround. However, the issue may occur in an environment with any drive manufacturer or host (Windows, Linux).
Problems related to Brocade's portCfgFillWord mode 3 can be solved with one of the following recommendations:
- Load tape drive code with the loop arbitration enhancement (CMVC 31077):
- LTO5_BBN0 and beyond
- TS1140 D3I3_5CD and beyond
- Change the Fibre Channel topology to point-to-point (N port), as loop arbitration does not apply to this topology.
- Change the Fibre Channel speed to 4 GBPS, as the Brocade fillword modes only apply to the 8 GBPS speed.