Very nice break down, Ed. This type
of situation is where the need for disk storage units becomes more and
more apparent. It's getting harder and harder to stream at the speeds faster
tape drives need to stay running at an acceptable level.
Just because the drive CAN go faster
doesn't mean it WILL, all other things remaining the same.
Not a knock on you, Simon.
Rusty Major, MCSE, BCFP, VCS ▪
Sr. Storage Engineer ▪ SunGard Availability Services ▪ 757 N. Eldridge
Suite 200, Houston TX 77079 ▪ 281-584-4693
Keeping People and Information Connected®
▪ http://availability.sungard.com/
P
Think before you print
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Ed Wilts <ewilts AT ewilts DOT org>
Sent by: veritas-bu-bounces AT mailman.eng.auburn DOT edu
04/07/2009 10:19 AM
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|
To
| "WEAVER, Simon (external)"
<simon.weaver AT astrium.eads DOT net>
|
|
cc
| veritas-bu AT mailman.eng.auburn DOT edu
|
|
Subject
| Re: [Veritas-bu] LTO4 Performance With
Exchange 2003 IS Poor |
|
On Tue, Apr 7, 2009 at 8:12 AM, WEAVER, Simon (external)
<simon.weaver AT astrium.eads DOT net>
wrote:
Environment:
NBU 5.1 MP5 Master Plus many SAN SSO Media Servers Win2k3 SP2
Problem: Mail Backups of Information Store using LTO4 SL500 are taking
4 1/2 hours extra to backup compared to LTO3.
If the tape drives were not your bottleneck before - i.e.
you were continually driving them at least 80MB/sec, then upgrading
to LTO-4 will likely slow your backups down. By my calculations,
you weren't bottlenecked at the tape drives. You were taking 4 hours for
1TB of data. That's a total of 69MB/sec. If you were doing
that to 3 drives, you were only averaging 23MB/sec per drive.
LTO drives must stream. If you can't feed them data fast enough,
you'll shoe-shine the drives with continuous start/stop fashion and performance
will suck.
Same configuration is in place
(ie: 3 streams to 3 different drives) and all part of the same fabric,
apart from being in a different building.
An IBM LTO4 drive requires a MINIMUM of 30MB/sec. An HP LTO4 requires
a MINIMUM of 40MB/sec. That's assuming no compression. If you're
compressing with a 2:1 ratio, you'll need double that. They top out
at 120MB/sec native and 240MB/sec with (2:1) compressed data.
So let's assume 2:1 compression on 3 streams going to an HP drive.
You'll need to deliver 2*3*40MB/sec, or 240MB/sec at an absolute minimum.
You can deliver up to 2*3*120 or 720MB/sec.
Since you were only averaging 23MB/sec per drive before,
you've got a LONG way to go.
.../Ed
Ed Wilts, RHCE, BCFP, BCSD, SCSP, SCSE
ewilts AT ewilts DOT org_______________________________________________
Veritas-bu maillist - Veritas-bu AT mailman.eng.auburn DOT edu
http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu
_______________________________________________
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