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RE: [nv-l] HACMP vs. backup managers

To: nv-l@lists.tivoli.com
Subject: RE: [nv-l] HACMP vs. backup managers
From: James Shanks <jshanks@us.ibm.com>
Date: Fri, 14 Mar 2003 09:03:30 -0500
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<soapbox on>
As, most everyone who subscribes here knows, I am a big fan of hot backup. 
 That's two simultaneously active NetViews.  The biggest reason is 
operations. I never met an operator yet who didn't understand "move to the 
other box" as a plan, but I have seen them screw up just about everything 
else that required a series of steps.  I was a systems guy at a customer 
site for 8 years, before joining IBM, and I used to have to write the 
backup procedures and train folks to do them.  In the end, success 
depended on who was the shift supervisor at the time of failure. 

It's relatively easy to have two NetView and keep them in synch, and even 
easier in 7.1 with the new hot backup facility (nvpause and nvresume), 
which allows you to pause the daemons, rather than stop them,  during 
whatever slack period you choose to make a copy of your databases.  Or you 
can just have two independent NetViews.  I have seen installations where 
in fact they have three.

The thing about HACMP that most folks don't realize is that NetView is not 
designed nor optimized for it.  The ideal HACMP secnario is the case where 
the running app can be killed and restarted on another box immediately 
with no recovery procedures required.  But that is not the case with 
NetView.  The daemons keep large amounts of data in memory, and if you 
suddenly crash the box, it is likely that the  databases are out of synch. 
 You will almost certainly have to do ovtopofix -A ( for one map or -a for 
multiples) BEFORE you start using NetView again, or else you risk the 
dreaded database corruption.   Ideally you would start everything but 
netmon and do that before continuing.  And since NetView "knows" where it 
is, you need to move not only the disks to the backup machine but also the 
network interfaces.  It can be done, and there folks doing it, but it is 
not trivial and there are plenty of possibilities for error.

A second NeView gives you the comfort of being able to continue operations 
virtually uninterrupted while you bring the failed box back up. Hardware's 
the cheapest part of the computing equation in the long run.  Buy a 
another box. 
</soapbox off>

James Shanks
Level 3 Support  for Tivoli NetView for UNIX and NT
Tivoli Software / IBM Software Group

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