[ADSM-L] 6.2.2 Backup Stgpool Performance issue?

OK, here's another oddity.
Customer upgraded from 5.5 on Win2K3,  to 6.2.2 on Win2K8, 32G Ram.
Tapes are 3 IBM LTO4's in a TS3310.

Everything works great, except we appear to have a problem with BACKUP STGPOOL 
running very slowly, on occasion, going tape to tape.

Other tape to tape processes (reclaim, for example) work fine.  BACKUP STGPOOL 
running from diskpool to tape works fine.  But on some days, BACKUP STGPOOL 
running from tape to tape appears to just hang.  The output from Q PROC below 
shows it hanging on the same "current physical file" of 122GB, for over 12 
hours, until we had to cancel it.

There were no other tape processes running, nor was expiration.  Over the 12 
hours there were occasional small client backups, but nothing intensive.  
Sometimes after 3-4 hours, the process will "break free" and pick up speed 
again, other days it won't.  Dedup not turned on.  At first I suspected a bad 
LTO cartridge or a firmware problem, but we've updated the firmware, and this 
occurs on so many different cartridges that we've ruled that out.  I'm stumped.

I've calculated MB/sec throughput for every combination of disk-to-tape and 
tape-to-tape processes and we are getting decent throughput, even on BACKUP 
STGPOOL, except for these occasional hangups.

Anybody seen anything like this?  Otherwise I'm thinking it's time for a PMR 
call and a trace...

>q proc

Process     Process Description      Status
  Number
--------     --------------------     
-------------------------------------------------
      64     Backup Storage Pool      Primary Pool ORA-LTO4POOL, Copy Pool
                                       LTO4VAULT, Files Backed Up: 322963, 
Bytes Backed
                                       Up: 2,178,940,551,897, Unreadable Files: 
0,
                                      Unreadable Bytes: 0. Current Physical File
                                       (bytes): 122,700,012,064 Current input 
volume:
                                       A00575L4. Current output volume(s): 
A00578L4.





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