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Re: [Networker] Weird parallelism issue?
2010-05-23 21:11:11
I think I know a bit about what happened now.
The server parallelism was set to 16. It queued up 16 streams, even
though there was only one active drive. 4 went to the drive, and the
other twelve resulted in "waiting for 12 writable tapes" messages. When
the initial 4 finished, others kept filling the slots (presumably
because they hadn't been assigned to the 15 initial slots).
After 30 minutes, it apparently times out the waiting slots and then
re-enters them, so I went back up to 10 waiting tapes.
I set server parallelism to 4, and when the next 30 minute period
occured, they all released their slots and now it isn't complaining
about waiting tapes, so the remainder of them should get moving on the
tape faster.
On 5/23/2010 6:58 PM, Brian O'Neill wrote:
I'm running 7.4.5 on a CentOS 4 box.
Normally my backups go to a VTL first, but the VTL is offline so I'm
having the backups go direct to tape tonight. I only have one LTO-3 tape
drive operating as well (usually it is used for cloning/staging, and the
second drive started acting up today as well).
When the savegrp first runs, 4 backup streams write to the tape as
expected for the device parallelism setting. But after the initial four
are completed, it looks like only a single stream is permitted. I'm not
sure what exactly is happening...it seems like each additional client
that was waiting for a writable Default tape comes out of that state one
at a time, with the mounted tape having to reverify its label each time,
thus slowing things way down.
I checked other parallelism settings I could find. Server is set to 16,
while savegrp is set to 0. Only one savegrp was running at the time.
Any ideas how I can speed this up?
-Brian
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