Re: TSM and LTO Throughput

2004-04-23 17:46:53
Subject: Re: TSM and LTO Throughput
From: Tab Trepagnier <Tab.Trepagnier AT LAITRAM DOT COM>
Date: Fri, 23 Apr 2004 16:45:53 -0500

I have a 3583-L72 with four LTO-1 drives connected via HVDS SCSI to a
pSeries 6H1.  I have two drives per SCSI chain.

Depending on the type of data, I see 15 MB/s per drive consistently, and
with highly-compressible data, peaks as high as 40 MB/s.  That performance
is perfectly adequate for our little company.

One trick I implemented back when the library was collocated, was to wire
the drives "odd & even".  That is, drives 1 and 3 were on one chain, and
drives 2 and 4 were on the other.  If you watch how TSM handles
reclamation on a collocated storage pool, you'll see the wisdom of that
configuration.  On non-collocated pools it doesn't matter, and my other
three libraries are wired "high & low"; that is, drives 1 and 2 on one
chain and drives 3 and 4 on the other.

Tab Trepagnier
TSM Administrator
Laitram, L.L.C.

"Coats, Jack" <Jack.Coats AT BANKSTERLING DOT COM>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
04/23/2004 03:38 PM
Please respond to "ADSM: Dist Stor Manager"

        Subject:        TSM and LTO Throughput

Ok, I have a winders 2K box with 6 SCSI-attached LTO-1's with TSM
but it has a dual xenon 1.7G set of processors, and 1G of ram with 2G of
swap space.

The LTO's are in a IBM 3483-L18.  There are two LTO's on each of 3
SCSI chains (they are 160 adapters, de-tuned to 80 in the adapter BIOS,
because the LTO's I have won't work at 160).  But even at that two LTO-1's
should not outpace a 80MB/Sec SCSI adapter.

What kind of throughput are you folks seeing with SCSI attached LTO-1's?

I am trying some timeing doing migrations right now.  If others are
interested I will report back.

Why am I asking?  I think I have some performance issues, just getting
to/from tape, and can't seem to figure out where to look to find answers!
You guys being a 'similar user base' have some similar stats, that could
tell me if I am working 'as designed' or far behind the power curve.

TIA ... Jack

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