I'm sorry to interject without having read the complete thread but
I wanted to share (remind of previous emails) that I had a problem
with my LTO on Solaris a while back. Turned out the HBA card was
failing, the A side was dropping in performance with no additional/errors
noticable which the B side of the card remained OK.

Be sure to eliminate the HW if you haven't already.

On Wed, Mar 07, 2007 at 01:29:56PM -0500, Joshua Baker-LePain wrote:
> On Wed, 7 Mar 2007 at 11:45am, Kenneth Berry wrote
> 
> >The computer mbthome is both the amanda server and client, it is a Dell
> >PE2650 dual Xeon processor, 2GB Ram. Tape unit is LTO3 on a dedicated
> >SCSI controller.  Internal HDD's are four SCSI ultra320 10K configured
> >as hardware RAID5.  On top of this 100GB RAID5 disk is LVM Volume00
> >allocated as shown below.  One additional internal SCSI ultra320 10K
> >drive of 300GB capacity is allocated to LVM Volume02 and usage can be
> >seen below.  All the internal HDD share a common percraid controller.  I
> >have an external RAID5 set of drives on an third SCSI controller which
> >LVM Volume01 resides.  It should not be a factor currently it is unused.
> >Over the past weekend I migrated all the /home data from the external
> >set of drives to the single large internal drive, thinking the external
> >drives were the problem.  But this reorganization made not difference.
> 
> Some quick things to look into:
> 
> 1) Benchmark your various volumes with both bonnie++ (single thread 
> streaming) and tiobench (multithreaded).  This will give you some baseline 
> numbers.  You can also play with multiple instances of dd.  I have no idea 
> how good those perc controllers are, as Dull tends to obfuscate them 
> compared to their LSI underpinnings.
> 
> 2) LTO3 is *fast*.  Reading from a 4 disk RAID5 should be able to keep it 
> streaming, but simultaneously writing to that same RAID5 is likely to be 
> *very* slow...  Actually, looking at your tape write speeds in the 
> original mail, they're barely where they should be.  LTO3 can throttle to 
> 1/2 its native speed of 80MB/s before it has to resort to 
> drive/tape-lifetime-degrading stutter-stop-restart behavior.  One thing 
> that significantly helps is increasing your blocksize from amanda's 
> standard 32KB -- I use 2MB.  This requires recompiling amanda.
> 
> >/dev/sdd1            141003764  36925740  96915448  28% /amanda
> 
> Erm, where does sdd fit in in terms of the LVM volumes?
> 
> Also, both of Jon's suggestions (spindle numbers and filesystem profile on 
> /home) are good ones to look into.  Again, you can do your own 
> benchmarking outside of amanda to get a more controlled look at what's 
> going on.
> 
> -- 
> Joshua Baker-LePain
> Department of Biomedical Engineering
> Duke University
---
   Brian R Cuttler                 brian.cuttler AT wadsworth DOT org
   Computer Systems Support        (v) 518 486-1697
   Wadsworth Center                (f) 518 473-6384
   NYS Department of Health        Help Desk 518 473-0773