Greetings,

Although I am not currently defragmenting my current DSU volumes, I
previously had ~4TB in a single DSU under NBU 5.1 . This volume was
running vxfs and did receive a couple of hundred "small <100MB" jobs
each day, with Full backups each evening.

I did notice fragmentation on the volume and tried a number of things to
resolve this to get greater performance.

Running a daily (time to run for no more than 5 hours) defrag, this
process was extreemly slow (took about 1 month to get satisfactory
results). It did however improve the performance of the DSU by about
20MB/s.

Later I ended up creating several smaller 1TB DSU's (all from the same
lun) with no defragmentation running. my process for ensuring the system
did not lose too much performance, was stop using one DSU and empty the
images from it. choice of fill with empty files and let nbu destaging
process take care of it, OR bpexpdate -copy <x>. The latter process was
the simplest. With the empty volume you then have no fragmentation,
although I would run defrag anyway (my sanity is not in question here).
        Note: Under NBU 6+ we can now just set the "Threshold" to 1 to
clear out de-staged images.

The fact of fragmentation was only a problem for us as our users
"required" several days of full images to be kept on the DSU, meaning
the system was allways near 70% full.

We have since changed out infrastructure , utilising more DSU space. I
have not yet investigated impact of fragmentation on the DSU's.

Adam Mellor
Senior Unix Support Analyst
CF IT TECHNOLOGY SERVICES
Woodside Energy Ltd.


-----Original Message-----
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of osonder
Sent: Wednesday, 13 February 2008 9:22 PM
To: VERITAS-BU AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Defrag DSU?


Ok. Thanx !!  :D 

Anyone else have som comments about this?

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