Re: [Veritas-bu] Real World NBU Buffer settings Win2k3

2010-09-16 06:34:16
Subject: Re: [Veritas-bu] Real World NBU Buffer settings Win2k3
From: "William Brown" <william.d.brown AT gsk DOT com>
To: "veritas-bu AT mailman.eng.auburn DOT edu" <veritas-bu AT mailman.eng.auburn DOT edu>
Date: Thu, 16 Sep 2010 12:33:14 +0200

We use 262144 buffer size everywhere for both NET_BUFFER_SZ and tape SIZE_DATA_BUFFERS (or Windows equivalent).  What I did find made a very large difference when I was benchmarking an LTO4 drive (which has a 4Gb FC interface) was switching between a 2Gb HBA and a 4Gb HBA – the throughput nearly doubled.  That was testing with ‘dd’ not NetBackup, but was going through the (Solaris) OS.  So I would see if there is any way that you can up the speed, even if you go point-to-point and not via a SAN switch to avoid having to upgrade your fabric [no use if you share the drives with SSO!]


For Windows on FC you should find any modern FC driver will use the tape buffer size that you set.  64k was with the Windows scsi driver, and for some SCSI cards you might have to adjust the MaximumSGList in the registry – ( and (  More recent Adaptec driver install kits I have noticed do this for you.  You should be able to see in the bptm log what size is being used.  The fact you say the tape would not mount if you change settings *is* suspicious.  Make sure you have the latest drive/robot settings files so your drives are properly set to variable block size.  Again bptm log should help.


If the data is compressed on disk then I assume the Windows OS is having to decompress on the fly as it reads the disk which is going to hit the client quite hard on the CPU.  Not much you can do about that, but FlashBackup would not have to do that so I’d say was worth trying.  Bear in mind it will back up the entire volume, so you don’t want to be backing up a lot of empty space (though paradoxically that empty space would compress nicely when it hits the LTO drive’s h/w compression, provided Windows is zeroing the blocks on file deletion…not sure if it does this or even can be made to…otherwise you have a great disk scavenger ;-) ).




From: veritas-bu-bounces AT mailman.eng.auburn DOT edu [mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of WEAVER, Simon (external)
Sent: 15 September 2010 19:00
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Real World NBU Buffer settings Win2k3


Hi All
Anyone got any real world experience on buffer settings:

Win2k3 San Media, connected to 2GB Fabric attached 8 LTO4 Drives.
Due to drive availability, Multiplexing onto one drive.

Main problem: One volume (1,7tb in size) takes over 4 days to fully complete.
Got the Tuning Guide and Technote 244602, but I tried some settings, only to find the backup would not even mount tape correctly.

So back to "no" settings at the mo.

Volume are generic files/folders, mixture of large and small sizes. But 1.7TB's in my view should be done quicker. Also Data is compressed.



This email (including any attachments) may contain confidential
and/or privileged information or information otherwise protected
from disclosure. If you are not the intended recipient, please
notify the sender immediately, do not copy this message or any
attachments and do not use it for any purpose or disclose its
content to any person, but delete this message and any attachments
from your system. Astrium disclaims any and all liability if this
email transmission was virus corrupted, altered or falsified.
Astrium Limited, Registered in England and Wales No. 2449259
Registered Office:
Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2AS, England


This e-mail was sent by GlaxoSmithKline Services Unlimited 
(registered in England and Wales No. 1047315), which is a 
member of the GlaxoSmithKline group of companies. The 
registered address of GlaxoSmithKline Services Unlimited 
is 980 Great West Road, Brentford, Middlesex TW8 9GS.

Veritas-bu maillist  -  Veritas-bu AT mailman.eng.auburn DOT edu