I think the minimum tape use you can achieve over 31 days with 10 levels and
no incremental function is arrived at using something like this:

0,1,1,1,2,2,2,3,3,3,3,4,4,4,5,5,5,6,6,6,6,7,7,7,8,8,8,9,9,9,9

It minimizes the accumulation. It should be the optimum arrangement if that
is the only parameter you are concerned about. If you are on 5 days instead
of 7 per week you can do a little better. 

-----Original Message-----
From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On
Behalf Of A Darren Dunham
Sent: Tuesday, January 20, 2009 10:33 AM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] NDMP Schedling

On Tue, Jan 20, 2009 at 10:22:39AM +0000, Davina Treiber wrote:
> A Darren Dunham wrote:
>
>> I'm not sure what you're saying about a level 1 acting as an 
>> incremental.  A level 1 and an incremental are different.  In a 
>> normal environment, consecutive level 1 jobs will require more volume 
>> space than consecutive incrementals.
>
> Not necessarily true. Although you will backup more data with a level 
> 1 than an incremental, you will need to keep more volumes to fulfill 
> the retention requirements. If you have a monthly cycle of 
> incrementals you will need to keep up to a month of extra incremental 
> backups, since the incrementals depend on all the other incrementals 
> all the way back to the previous full. With a monthly cycle of level 1 
> backups the level 1 backups will expire at exactly the time when the 
> retention period is reached, depending only on the full.

I'm not suggesting that such a scheme is better or worse than another
overall for all workloads.  But with NDMP, it becomes very difficult to do
true incrs for an extended period of time even if you want to.  I have one
server that I *really* want to.

I don't have any Celerra units, but I've heard that they have a true incr if
asked to do a "level 10" backup.  I don't know if Networker could ask for
that via NDMP or not.  Netapp filers don't have a similar facility.

--
Darren

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