It doesn't sound like a bus or tape drive issue because you're able to spin
the drive with a single stream at 30MB/sec.
First, how are your filesystems configured?  Are they striped and if so is
it a S.A.M.E (Stripe And Mirror Everything) configuration or is each
filesystem striped across separate hypers?
Then you should look at spindle contention.  When you run your 4 streams at
once how is it hitting your hypers based on the volume configuration from
above?  Then you'll need to map the hyper volumes back to the physical
spindles themselves.  This will help reveal if you've got some hot disks.  A
great tool for this is WLA (Work Load Analyzer) that EMC provides.  If you
don't have it configured at your site, get it.  It can be invaluable for
identifying performance issues on an EMC frame both at the disk level and
bus level.

-Dave

-----Original Message-----
From: Lee, Kenneth [mailto:Kenneth.Lee AT sbs.siemens DOT com]
Sent: Wednesday, October 22, 2003 10:13
To: 'veritas-bu AT mailman.eng.auburn DOT edu'
Subject: [Veritas-bu] one stream vs 4 streams


Master/Media server:  Solaris 8 - NB DataCenter 4.5 MP3
Tape drive:  STK9940B 
Disk:  EMC

I am running a backup on some file systems on EMC storage, total size is
about 500GB, on the master server.  If I used one stream and one tape drive,
I get a transfer rate of about 30 MB/sec and it takes about 5 hours.  When I
break it down to 4 streams and use 4 tape drives, I get 4 jobs with a rate
of about 7MB/sec and still take 5 hours.  It looks like the transfer rate is
divided by 4.  How can I get all 4 jobs to go faster and where can I look to
see why?

Thanks,
Ken

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