Networker

Re: [Networker] Query in Staging from adv_file

2008-08-21 09:07:27
Subject: Re: [Networker] Query in Staging from adv_file
From: Stan Horwitz <stan AT TEMPLE DOT EDU>
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Date: Thu, 21 Aug 2008 09:00:32 -0400
On Aug 20, 2008, at 9:41 PM, Peter Viertel wrote:


Getting back to the subject at hand, one thing confuses me
about using
an ADVFS. We have a Sun X4500 with Solaris 10 as a storage
node that's
fibre channeled into a large tape library that's shared by our
NetWorker server. I routinely see speeds writing to that device of
around 70-90MB/s but usually when it dumps to Sony S-AIT1 tape, the
tape's throughput hovers around 45MB/s. While a staging
process is in
progress, no data can be recovered from the device. Our X4500 has a
1Gige line going into it, as does our NetWorker server.

I have two questions to follow up on what was said earlier.
Is 45MB/s
reasonable to write to tape and am I wrong in assuming that one can
never recover data from an ADVFS while its busy staging data
to tape,
or have I misconfigured this set-up?


Two answers for you, both leave us with questions however:

1. staging...

One thing we discussed a couple of months back was that if you are
restricting pools to devices - like you do when you have adv_file and
tape devices is that you need to make sure that both the real device and
the RO device are owned by the same pools. If you don't do this then
there will be contention between restores and cloning operations.

Or that was my recollection of this at least... I have yet to sit down
with a test system and nut out the mechanics behind this - has anyone
else worked through the different configs?

2. AIT-1

I know nothing much about AIT - so I went looking on the sony website...
Here's what it tells me...   AIT-5 is the latest generation of this
technology - the drives can sustain data transfer rates around 80MB/ sec
and they store 400G native - so these are roughly equivalent to LTO3.
you say you have AIT-1, the spec sheet says the tapes only store 40GB
native, the transfer rates is a measly 6MB/sec - which makes them the
equivalent of DLT8000, in other words AIT-1 drives should be in a
museum... If you're seeing 45MB/sec then either you've got later drives and tapes than AIT-1, or the compressibility of your data is very good.

If you really do have AIT-1 drives then they are a mismatch for your
nice thumper system, if you want read-compatibility you can upgrade as
far as AIT-3T, it looks like AIT-4/5 can read 1...

I got all this from here.... http://sony.storagesupport.com/node/7176
I shall remain happy that we went with LTO.

I am using SAIT-1, not AIT-1. I routinely see 70-90MB/s on my tape drives when doing direct backups (no advfs involved) for multiple sessions. The RO and writable parts of the advfs are both owned by the same tape pool.

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