Veritas-bu

[Veritas-bu] 6.0 DSSU Behavior

2007-01-24 15:10:58
Subject: [Veritas-bu] 6.0 DSSU Behavior
From: JMARTI05 at intersil.com (Martin, Jonathan (Contractor))
Date: Wed, 24 Jan 2007 15:10:58 -0500
Configuring a few DSSUs on 6.0 MP4 and I wanted to bounce this off
someone who has possibly been there before.

What are the advantages / disadvantages of assigning multiple DSSUs to
the same volume?

Example - I've got a 2TB volume on a media server (/array or E:\) that
has two folders on it, DSSU1 and DSSU2.  Both are configured with a 98%
High Water Mark and 80% Low Water Mark (defaults.)

Now it seems to me that if planned carefully, this could work.  As the
disk fills up to 98%, say writing several jobs to DSSU1 the system will
constantly expire old images until the entire volume is at 80%.  Lets
say those are backups for week 1.  Week 2 and 3 run similarly.  Then
comes week 4.  On week 4 I want to write the same set of backups to
DSSU2, which points to another volume pool because these tapes do not go
to the same place as DSSU1's tapes.  But there is only 20% free disk
space.  When I start writing to DSSU2, and it gets to 98%, what happens?
If I'm reading the documentation correctly, both DSSU1 and DSSU2 will
start expiring images until the volume gets down to 80% free disk space,
is that correct?

Would this be any different if I wrote to both DSSUs simultaneously?
Once free space was less than 2% wouldn't both DSSUs go into action
expiring data?  I guess to simplify I could create two 1TB volumes and
assign each accordingly, but I just can't get around wanting that extra
"buffer" space.

Comments / suggestions?

Thanks,

-Jonathan

PS: The specced out "substandard" backup system is actually performing
well and I'm working on writing a nice long detailed email about how I
got it all to work. :)


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