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Periodic tape backup throughput issues

I’m having a perplexing throughput issue with my tape backups.  Every two weeks (on a Tuesday for the past two months) my tape backup throughput decreases dramatically – from 1,360 MB/min to 130 MB/min.  The speed decrease happens regardless of the source of the backup – over the LAN or running a duplicate job where the backup-to-disk folder is stored on the backup server hard drive.  This situation does not impact the speeds of disk-to-disk backups.  The only way to resolve the issue is to reboot the backup server.  Below is my configuration.
Dell PowerEdge 2850
Dell PowerVault 124T LTO-3
Adaptec 39160 SCSI adapter
Windows Server 2003 Std x64 SP2 fully patched
Backup Exec 2010 fully patched
Troubleshooting steps I’ve taken

  • contacted Symantec who had me run various diags
  • contacted Dell who had me upgrade the firmware for the tape/autoloader
  • checked to make sure there are no scheduled tasks running during this time
  • checked Task Manager for processing consuming CPU or generating lots of I/O – none found
  • compared running processes to server after reboot – no differences
  • rebooted server for several consecutive days to see if it would extend the interval – it did not
  • verified all the drivers were at the latest levels – tape, autoloader, SCSI adapter
  • checked Windows Application and System logs for errors – none found
  • checked tape autoloader logs for errors – none found
  • checked tapes for errors – none found
Anyone have any ideas what could be causing those or what other steps I could take to troubleshoot the problem?
6 Replies

Usually this kind of periodic

Usually this kind of periodic problem is due to some periodic housekeeping job that runs at this particular time.  This job may be holding some resources or chewing up the CPU cycles.

HBA firmware?

Is your HBA firmware at the latest level?  It kind of sounds like the SCSI bus may be negotiating down to a slow rate until you reboot the server.

I've been working with Dell

I've been working with Dell Tech Support and have verified that the HBA firmware is at the latest level.

Does stopping & restarting BE

Does stopping & restarting BE services resolve the issue?  Or must you actually restart the whole server?

We need to restart the whole

We need to restart the whole server.  Dell may have isolated it to a hardware issue.  The condition raised its ugly head today.  Dell is running ITDT diags against the tape drive.  The performance test is taking an unusually long time.  Hopefully the logs will tell us something when the test finishes.

Any resolution?  Was this a

Any resolution?  Was this a hardware issue?