Re: [Veritas-bu] Real World NBU Buffer settings Win2k3
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 (http://h20195.www2.hp.com/v2/GetPDF.aspx/5982-9971EN.pdf). 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,
Sent: 15 September 2010 19:00
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Real World NBU Buffer settings Win2k3
got any real world experience on buffer settings:
San Media, connected to 2GB Fabric attached 8 LTO4 Drives.
to drive availability, Multiplexing onto one drive.
problem: One volume (1,7tb in size) takes over 4 days to fully complete.
the Tuning Guide and Technote 244602, but I tried some settings, only to find
the backup would not even mount tape correctly.
back to "no" settings at the mo.
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.
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