Veritas-bu

[Veritas-bu] LTO3 and Disk Staging

2006-09-22 09:41:00
Subject: [Veritas-bu] LTO3 and Disk Staging
From: Philip.Weber at egg.com (Weber, Philip)
Date: Fri, 22 Sep 2006 14:41:00 +0100
I've done lots of dd tests to/from the disk outside of NetBackup, using
individual LUNs and various filesystems configured in various RAID
configurations.  Also going by the manufacturer's spec sheets sa to what
I can expect max (150 Mb/s).  Performance issues manifest themselves as
soon as I try to write multiple streams to a disk staging filesystem
whilst also reading off it, though the attempted speed of the writes is
probably greater (from /dev/random) than I would expect from my
NetBackup clients.  But it's only got ATA drives.  Because the
performance is bad before I bring NetBackup into the mix, I haven't
looked much at tuning NetBackup yet.

My fastest backups are across the SAN fabric using Advanced Client & 4
streams will run to 1 tape driving it at about 50 Mb/s which may be the
drive limit (LTO2).

-----Original Message-----
From: Ed Wilts [mailto:ewilts at ewilts.org] 
Sent: 22 September 2006 12:37
To: Weber, Philip
Cc: veritas-bu at mailman.eng.auburn.edu
Subject: Re: [Veritas-bu] LTO3 and Disk Staging


On 9/22/2006 4:19 AM, Weber, Philip wrote:
> What sorts of disk systems are people using as disk staging to keep
> LTO3s happy?  

We're using HP EVA with FATA (Fibre ATA) drives.  We don't drive the 
LTO3s at full speed, but I do not believe it's an EVA issue.

> Our current EMC Clariion Cx300 struggles to supply data fast enough
> to 3 LTO2 drives (even outside of NetBackup) and performance goes
> through the floor if (as is often the case) it is still trying to 
> write backups to disk while streaming data off to tape.

What sorts of benchmarks have you done to prove that it's a disk issue? 
  Have you done something like a dd to see how fast you can read data 
from the disk?  Have you monitored your switch ports?  I've witnessed 
our NetBackup environment hit 150MB/sec on our master server's 2Gbps 
switch port doing a dd from the DSSU to /dev/null.  My destaging 
performance to LTO-3 is normally quite poor so I know I've got a 
NetBackup issue somewhere.

> We have pretty much a 24*7 backup window with lots of slow & small,
> slow & big, and some fast, clients.

I think that describes most of us...  Do your fast clients drive the LTO

directly at a good speed?

        .../Ed

-- 
Ed Wilts, Mounds View, MN, USA
mailto:ewilts at ewilts.org


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