My setup is the same, all drives to all
servers.
If you are using a drive and the SAN media
server is not in need of a second one, why would it keep scanning all the
drives?
I have had drives go down for some reason
or another, but it only goes down on a media server that tried to use it.
So say I have 4 servers who can use a
drive.
Server A tries to use it and it has
issues, server A downs the drive.
If you look at the drive, it is now mixed,
as only server A has it down, the other three still show it up.
Now say server B tries to use it, so
server B downs it. The drive is still mixed, two servers saying down, and
2 servers who have no clue because they have not used it.
This makes me think that it does NOT try
to look at drives unless it tires to use it.
I may be wrong, but based on what I have
seen, I don’t see where the server is checking the other drives if it
does not need one.
From:
veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Geyer, Gregory
Sent: Tuesday, January 06, 2009
11:20 AM
To:
veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] assigning
only a portion of tape drives to mediaservers
We have all our tape drives (20) assigned to all our
media servers (3 main ones, and ~45 that server as SAN media servers, backing
only themselves up).
Dealing with tape drive throughput issues and we've
had a Brocade support person tell us that this setup is not ideal and that even
when a tape drive has been granted to a host and it starts to use it, that its
checking on the other tape drives prevents good throughput. He says to
only assign about 4 drives per media server.
This does not seem right to me, but hey, I'll check
out anything. My understanding is that 6.5 (we're at 6.5.2a, about to go
to 6.5.3) has a centralized device database and that the design of a SCAN_HOST
performs the gatekeeper roll for the tape drives.
I've added a new server and only configured 4 drives
to run a test on it. Of course it is queued up waiting for a free tape
drive, and there's been 147 other jobs that got a tape drive while it's been
queued up...(proving point #1 for why all servers had seen all drives).
If you have any opinions on Brocade's theory (or at
least our SAN guy's interpretation of it - this is all 2nd hand) I'd be happy
to receive it.
