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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.
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