Re: [Veritas-bu] assigning only a portion of tape drives to media servers
2009-01-06 14:17:12
On Tue, Jan 6, 2009 at 11:20 AM, Geyer, Gregory <Gregory.Geyer AT avnet DOT com> wrote:
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. Pre-6..0, every host was responsible for managing the tape drives, and the master would constantly poll each media server for what was going on. Starting at 6.0, the master took total responsibility for it and simply tells the media server which media to mount on which device. Media servers became a lot dumber, and that's actually a good thing.
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.
I think his data is dated and the suggested changes are not going to help with throughput at all but hurt you in device availability as you've already discovered. As a result, the total amount of data you'll be able to push through will decrease, not increase.
.../Ed
Ed Wilts, RHCE, BCFP, BCSD, SCSP, SCSE
ewilts AT ewilts DOT org
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