Networker

Re: [Networker] Question on target sessions?

2006-07-20 19:49:36
Subject: Re: [Networker] Question on target sessions?
From: George Sinclair <George.Sinclair AT NOAA DOT GOV>
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Date: Thu, 20 Jul 2006 19:47:46 -0400
Thanks, Tim. I played around with disabling the other drives and/or
simply un-selecting them from the given pool resource. Either of these
seems to accomplish the same thing wherein NetWorker will send how ever
may save sets it wants to the device (the one tape) and not pay
attention to the target sessions value of 4.

I did try changing the group parallelism to 4 with all the drives
enabled and all the devices selected for the pool, and this works
nicely. NetWorker maintains a steady stream of 4 save sets rather than
doing 4, completing, and then starting the next 4, etc. like it does if
I have the group parallelism set to the default of 0.

This brings up a question here. Let's suppose that I had say 10 clients
in a group, with anywhere from 3-4 save sets each, for a total of say
30-40 save sets. If I expect to have 3 tapes always available, and I
want to limit the target sessions to about 4 (I like to keep it at 4-5
max to decrease recover time) on the devices, then that's 3*4=12, so if
I make my group parallelism 12 then would that keep a stream of 4 per
device? What if I only had one tape available? Would it try to send 12
sessions to that one device?

I just want to keep a stream of x sessions going to every device that's
available where x is the target sessions on the device (typically 4-5),
but I don't want NetWorker to exceed that too much if it only has one
drive available.

Thanks.

George


Tim Nicholson wrote:
> I have not had this particular one happen, but something similar.
> 
> It seems that
>     if you have another device available for the pool, even if
>     that device is offline,
>     and you have used up the target sessions for all other devices
>         currently in use for that pool
>     then NetWorker queues save sets for a volume, which it expects
>     would be mounted on a new device.
> 
> This would mean explain your situation (and some others).
> 
> Our solution was to only put the devices that were really
> available in the "devices" attribute of each pool's resource.
> 
> In your case you could also just change the "group parallelism" to 4.
> 
> 
> 
> On 21/07/2006, at 7:31 AM, George Sinclair wrote:
> 
>> Hi,
>>
>> Why is it that if the total number of save sets for a group exceeds the
>> value of the drive target sessions (in our case 4), and you only have
>> one writable tape, NetWorker will wait until the first 4 save sets have
>> completed before sending the next pending ones to tape?
>>
>> NetWorker does ask for a second writable tape, and yes, if I had one
>> available, it would mount it, and then it would be writing 4 save sets
>> to drive 1 and 4 to drive 2, but I don't understand why it can't start
>> sending save sets that were previously pending to drive 1 as soon as one
>> of the running save sets completes. Instead, it seems to want to wait
>> until all 4 are complete, it then pauses for a minute and then continues
>> with the next 4, and so on. Is this normal behavior? It would be nice if
>>  it could send stuff there as soon as something frees up and not wait.
>>
>> We have 7.2.2 running on a Solaris test server, using a Linux storage
>> node. The tape library is on the storage node. It has 4 SDLT 600 drives,
>> each set to 4 target sessions, but I currently have only one writable
>> tape. The parallelism for the clients is set to default of 4, and the
>> server's parallelism is 20. I have a group of 8 clients and a total of
>> 10 save sets for this test.
>>
>> Thanks.
>>
>> George
>>
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