Veritas-bu

[Veritas-bu] LTO vs M2

2003-02-20 12:21:20
Subject: [Veritas-bu] LTO vs M2
From: vaxzilla AT jarai DOT org (Brian Chase)
Date: Thu, 20 Feb 2003 09:21:20 -0800 (PDT)
On Wed, 19 Feb 2003 Karl.Rossing AT Federated DOT CA wrote:

> I'm thinking of dumping our Mammoth(m1) library in favour of a library
> with LTO ultrium 230 drives.
>
> I'm currently seeing thruput of 4400KB/sec in my veritas console for 20GB
> db partition. The library and the db partition are located on the same
> drive. The backup is not multiplexed.

Do you mean that the NetBackup catalog and your database partition are
located on the same hard drive?  Also, are you talking about a true
"hard drive" (single spindle) or is this data located on some type of
RAID device?  If you're talking about slow performance while backing up
from single disk drive that's seeing I/O requests from multiple sources,
you're most probably bottlenecking at the disk drive and not your tape
drive.  You should also understand what's happening on any relevant SCSI
or FC busses, and also the busses further up the tree like the PCI
busses.

> What kind of speed can i expect for the LTO backup?

Assuming there are no bottlenecks in I/O path from the disks which are
bing backed up to your tape drives, I've found LTO to perform
exceptionally well.  The majority of the data where I work is already
compressed image data, so our tape transfer speeds reflect the bottom
end of what LTO is capabale of pushing.  I'm very consistently seeing
13-15MB/s on most of our backups; the exceptions being when the data is
coming from a server that's networked with 100Mb/s ethernet, or on
servers that are already under a heavy load.

Still, the most important thing is to make sure all of your I/O is
balanced appropriately.  In my case, with our data being compressed
already, I planned for 1x 1Gb/s network connection for every four LTO
drives.  So, depending on your needs and you're environment, you can
either split the drives and networking up across multiple media servers.
I've found that a single SunFire V880 combined master/media server can
easily handle feeding 8 LTO drives while doing the bookkeeping for
a few thousand backups every day.  We're pushing anything from several
hundred GB to a couple of TB each day.

Other advice would be to go with the IBM drives if that's an option.
I've been running them for almost a year now without problems.  At a
previous employer, I'd been using IBM's 3590 drives.  Their tape drives
are second to none (I've never regretted paying a bit extra for their
drives).

-brian.


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