Probably most customers using Data Protector with a Fibre Channel Tape Library attached expierienced this problem: a SCSI Reset during the backup including destroyed media. What happened? The drive was flooded with SCSI commands – device polling was the cause.
Polling is the behaviour of a service which polls tape drives and library controller via IFC (Interface Controller) or NSR (Network Storage Router) using SCSI commands frequently. This may influence running backups, as the NSR must process additional commands, which mostly come not from the backup software.
Results
- Changed backup speed
- I/O errors
- The backup software recognizes the media as poor
- A tape drive will be set to offline
- The transfer rated decreases
- The tape drive can not stream
Known serives causing these errors:
- Network scanner
- Removable Storage Manager
- Tape driver
- OVOSAM using old Tachyon drivers
- Insight Management Agents (SIM)
- Retrosopect / Retrorun (Macintosh)
Recommendation: Deactivate polling on all servers where tape drives are attached.