Networker

Re: [Networker] Maximum number of save sessions?

2007-03-17 10:56:52
Subject: Re: [Networker] Maximum number of save sessions?
From: Rick Brode <rbrode AT COMCAST DOT NET>
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Date: Sat, 17 Mar 2007 08:43:43 -0600
George,

By removing the fulls generated by the test, you did leave a gap. It sounds like your situation is something like this:

real Full
real Incr 1
TEST FULL
real Incr 2:

By removing the "TEST FULL" backups from the databases, any files modified between the "real Incr1" and "TEST FULL" backups have not been backed up on the involved clients.

Since you already deleted the "TEST FULL" information from the databases, the easiest solution would probably be to do a level 1 backup on the effected save set. That would get the missed files and not impact future incrementals. However, depending on the number of days between the "real Full" and "TEST FULL" backups and the amount of data change in the file system during that period, you may not want to do a level 1. Another solution might be to remove all the savesets after the "real Incr1" backups from the databases using "nsrmm -d -S ssid" (use mminfo to get the ssid's) and then rerun the incrementals on the effected save sets.

Lastly, you could hope that no recoveries of the missed files will be needed, and do nothing. :-)

Rick

=====================
Rick Brode
Brode Training and Consulting
EMC NetWorker Training
www.brodetraining.com


George Sinclair wrote:

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



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