Networker

Re: [Networker] Protecting specific volumes / pools

2006-09-13 12:25:53
Subject: Re: [Networker] Protecting specific volumes / pools
From: Steve Warren <swarren AT cresend DOT com>
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Date: Wed, 13 Sep 2006 11:17:55 -0500
One problem is dependencies can make tapes unavailable for automatic
relabeling even though retention says they ought to be available.

For example if you have a week-long chain of incremental tapes, all it takes
is for one client in the chain to miss its full backup the prior weekend to
hold up relabeling of the whole chain of tapes when it's time for them to be
recycled. None of the tapes at the beginning of the chain can be recycled
until all the tapes at the end of the chain are recyclable. Each weekend
that any client misses its full will potentially add another week to the
retention of the tapes at the head of the chain.

It's not an impossible problem but it's something you have to manage if you
have a just-in-time tape management solution. There's the potential to get a
set of tapes back that really need to be used on a particular day, but
NetWorker may refuse to consider any of those tapes for mounting, because
they're part of an extended dependent chain.

The dependency is real. If you manually relabel tapes in a dependent chain,
at least one client will probably not be fully recoverable from that day
forward to the next full backup of that client, because it really did depend
on tapes in that chain to be able to recover. That's why NetWorker doesn't
want to relabel them.

The best solution is to pay attention when a client misses its full and make
it up the next day. Worst case your retention gets stretched an extra day.

-----Original Message-----
From: Law, Steve [UK] [mailto:Steve.Law AT CGI-EUROPE DOT COM] 
Sent: Wednesday, September 13, 2006 9:37 AM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: Protecting specific volumes / pools

 Hi,  

Thanks for your responses, Will and Davina.

I think the crucial issue here is that we are contracturally obliged to
off-site our tapes on a daily basis. The tapes are brought on site when
required and removed the next day. This is to protect them in case of a
disaster, doesn't everyone do that? What about if a meteorite turns your
building into smouldering rubble?

Davina has stated that with regard to the relabelling, there's no way to
prevent someone relabelling a volume if they really want to; I was
hoping for something like a setting within the pool config that
prevented relabelling, making it only possible if your reconfigured the
pool's settings). But your responses have made me realise that the
relabelling we do is unnecessary. 

We took over the management of these backups when our storage guy left
suddenly, and we kind of made it up as we went along. He used to keep
approx 150 tapes constantly in the library and clone those that were
written to overnight, to be take offsite for a period then eventually
merged back in. This made monthly backups (that are permanently archived
offsite) very messy because Networker would write to a number of tapes
that had space on them, some of which had lots of other data from
previous backups on too. So we basically changed everything to a simple
system we understood (Networker is very different than anything else
I've used).  

Obviously, so it seems to me now, if we change the browse and retention
times of the bi-weekly and 4-weekly backup jobs so the save sets expire
a day or two prior to their re-use, then the Operators won't need to do
anything (which they'll like). But if for the Notes/SOX compliant
backups we keep a browse/retention time of 7 years they'll never be
overwritten just appened to.  

If we do stop relabelling and change the browse/retention times, then
the only tapes we'll ever label will be the month-end ones, which are
new tapes used once and then phyically labelled and indefinitely
archived. As they will be brand new never-before-used tapes there won't
ever be any need to delete the volume objects in the Networker db, which
is the only way the Notes/SOX tapes could be overwritten. We could even
label the Notes/Sox tapes as "NEVER_DELETE_ME_MONDAY" etc.

That's right, isn't it?


Thanks again,



Steve Law
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