Veritas-bu

Re: [Veritas-bu] Inline Tape Copy vs Storage Unit Groups (and other ITC wierdness)

2009-04-24 10:05:06
Subject: Re: [Veritas-bu] Inline Tape Copy vs Storage Unit Groups (and other ITC wierdness)
From: Girish Jorapurkar <girishsj AT yahoo DOT com>
To: VERITAS-BU AT MAILMAN.ENG.AUBURN DOT EDU
Date: Fri, 24 Apr 2009 07:01:58 -0700 (PDT)
Storage unit group is, typically, used for load-balancing jobs across mutliple 
STUs - possibly residing/attached to different Media servers.

Inline-tape-copy creates multiple copies at 'backup time' by writing each copy 
to a different media from STU(s) attached to same Media server. Essentially, it 
receives a tar stream from a client to the media server and, then, hands out a 
copy to each media on the server. There are couple of points to note: (a) it 
will use as many drives (if tape is used) as copies being created, (b) all 
copies get created in-sync; so the backup speed for all copies is determined by 
the slowest one in the set.

So, when ITC is pointed to STU group, the load-balancing will take backseat 
since each copy needs a STU (in the group) from a common Media server. And, 
that may result into undesired performance implications. The warning just 
highlights that it is not a best practice to do so.

Depending on what version of NetBackup you have and your business requirements, 
you may want to look into disk-staging/duplication (6.0), Storage Lifecycle 
Policy (6.5.x) to create multiple copies.

/Girish



----- Original Message ----
From: "Donaldson, Mark" <Mark.Donaldson AT Staples DOT com>
To: VERITAS-BU AT MAILMAN.ENG.AUBURN DOT EDU
Sent: Thursday, April 23, 2009 1:18:36 PM
Subject: [Veritas-bu] Inline Tape Copy vs Storage Unit Groups (and other ITC 
wierdness)

If I create a policy that uses inline-tape-copy to make an offsite copy,
I see two pieces of wierdness that I don't understand.  

The first is that if I select a storage unit group for my destination,
the tape pool, tape owner, etc. grays out.  It's not like my tape pools
are tied to a specific server, they're all setup for *ANY* server so
that shouldn't be an issue.

A work-around seems to be to use a regular STU at first, set-up
everything, then go back and change it to a STU-Group.  When you do
that, it warns, in a pop-up box, "Warning. Selecting storage unit groups
for multiple copies can severely impact performance."

Anybody know the why's and wherefores of these things?

-M
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