[Networker] Maximum number of save sessions?
2007-03-16 21:12:41
Hi,
We're running NetWorker Network edition 7.2.2 on a Solaris server with
two Linux storage nodes. Each snode manages one tape library. There are
no tape devices on the server, but there are 3 file type devices. Are we
indeed stuck at a maximum of 32 save sessions per storage node?
I know with the Network edition that our maximum server parallelism is
96 (32 + 2*32 since we have 2 storage nodes). Also,
I guess our total devices can be 48 (16 + 2*16 for each snode), but
someone recently mentioned that having the extra
snode license doesn't require you to have to have the snode itself and
that this would then increase the number of devices you could
support on any one snode from 16 to 32, so if you had two snode licenses
but only one snode and one attached library, you could
conceivably have 32 devices on there? Not sure if that's the case, but
if so, does the same thing hold true for save sessions per snode?
Kind of a bummer that our server can support up to 96 sessions but we're
stuck at 32 for each snode?!!!
** The reason I ask ***
I'm still testing out these LTO3 drives, and I've found - and it's
probably no surprise - that in order to push the drives to a reasonable
performance level (even 50-60 MB/s), I have to increase the target
sessions to about 12. This wasn't the case before with the older LTO1s,
where we typically used 4-5 target sessions, and we're getting decent
performance from our SDLT-600 drives, running on the other snode, at 5
sessions each for a total of 20. But we're backing up directly over
gigabit ethernet, so we don't have a front end VTL, or some such thing,
where the network can be taken out of the equation - at lease not yet.
I found that once I hit 16 sessions, the LTO-3 drive could easily top 80
MB/s, but at 12, it averaged anywhere from 50-60 MB/s, hitting upwards
of 73 MB/s sometimes. Of course, it screams when backups are run from
the host itself (99 MB/sec or better), but with gigabit ethernet, I'm
probably lucky to get 95 MB/s coming in to the snode period. The SCSI
HBAs can handle the load (they're dual channel 320 MB/s each, total =
640 MB/s), and the snode host can handle it, but I can't push data fast
enough to make the drives really burn unless I up the target sessions.
If I do that, though, then I would quickly exceed the 32 session limit
when carried out over 4 drives. That's a bummer. I know upping the
target sessions will increase recovery time, and not sure if the faster
read speed on LTO-3 drives would compensate?
I'd like to add 4 more drives to the library for a total of 8, mostly to
allow cloning operations that might run in parallel with the backups. I
thought having more drives would help out. Right now, with 4 drives, all
the drives are typically in use once the backups are running, so cloning
other tapes would have to be done during the day, which is fine but it
could overlap into the evening and effect backups or vice versa since
various drives that might otherwise be available would then be in use.
But even with only 4 drives, it seems I would be limited to 8 sessions
each, for a total of 32?
George
--
George Sinclair - NOAA/NESDIS/National Oceanographic Data Center
SSMC3 4th Floor Rm 4145 | Voice: (301) 713-3284 x210
1315 East West Highway | Fax: (301) 713-3301
Silver Spring, MD 20910-3282 | Web Site: http://www.nodc.noaa.gov/
- Any opinions expressed in this message are NOT those of the US Govt. -
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