On Wed, 17 Aug 2005 19:04:23 +0100, Davina Treiber <Treiber AT HOTPOP DOT COM> 
wrote:

>Ronquillo, Merill CONT (NAVFAC) wrote:
>> Just trying to understand more about adv_file type devices. Suppose I 
have a pool of 4 adv_file devices. Server parallelism is 64, target 
sessions on each disk device is 8. If I understand target sessions 
correctly, this is how the data gets backed up:
>>
>> Volume1 gets savesets 1-8
>> Volume2 gets savesets 9-16
>> Volume3 gets savesets 17-24
>> Volume4 gets savesets 25-32
>> Volume1 gets savesets 33-40,  THIS IS WRONG (even for tape devices)
>
>Volume1 gets SS 33
>Volume2 gets SS 34
>Volume3 gets SS 35
>Volume4 gets SS 36
>etc.

Interesting. I thought the save sets would go to each device in batches of 
8.

>> What would happen if savesets 1-8 fill up Volume1 and there's space 
remaining on Volumes 2-4?
>Save sets 1-8 will wait until space on Volume1 is reclaimed by staging
>or deletion. Save sets to adv_file devices do NOT span between volumes.
>Ever.

>Would savesets 33-40 be backed up to Volume1 after data already residing
>on the volume is automatically staged
>SS 33-40 will go to whatever devices are available at the time, although
>if a device is full and waiting for space, no new save sets will be sent
>to that device.

I'm thinking SS 33-40 will wait for Volume1 to stage. I completely forgot 
that ADV_FILE devices are never marked as full, so NW probably wouldn't 
know to send the data to a "free" device.

>Or will Networker see that Volume2 has free space and send 33-40 to that
>volume?
>It is very unlikely to send all these sessions to the same device, it
>will spread them around based on current sessions and target sessions.
>The amount of space remaining is NOT what governs where the save sets
>will go, except possibly in the case where all devices have exactly the
>same number of sessions saving to them.
>
>This is all a little academic, since multiple adv_file devices in the
>same pool is not the recommended way of setting things up.
>

We actually don't use the implementation I described. We've got 15(!) 
groups and 10 adv_file devices each with their own pools. But could you 
explain why having a single pool of disks is not recommended? Thanks.

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