Re: [Networker] Volume capacity?

Tim Mooney wrote:

In regard to: Re: [Networker] Volume capacity?, A Darren Dunham said(at...:

On Fri, Mar 19, 2010 at 05:04:58PM -0500, Tim Mooney wrote:

In regard to: Re: [Networker] Volume capacity?, George Sinclair said(at...:

Well, one reason would be that if on average you're getting 2:1
compression then NW will report the tape at 100% when it's only
written,  say, half of what it will end up writing, right?


That's true, but I guess I don't consider that a useful reason to change
the default volume capacity.


The only thing the capacity figure is for is reporting, so what would be
a more useful reason to change it?


Perhaps you and George are right, and I should be updating the default
volume capacity, since we too use device compression.  This may be one
more instance of "old habits" that should be revisited to see if it
still makes sense for my environment.

Your point about a volume being "full" no matter what % of the default
capacity was used is also salient.  I have this vague recollection that
there used to be an easy way to detect tapes that had bad spots on the
media (and therefore became full prematurely) using either the old green
GUI or some other obvious method, but perhaps not.  In any case, it
doesn't matter -- the way the product works now, it probably is worth
considering updating the default capacity if hardware compression is in
the mix.

We are using device compression and always have, but we're notnecessarily "using the 800 MB/tape number to track jukebox capacity". Ithink I was mainly just interested in having the reported value becloser to what's actually happening - kind of an aesthetics issue morethan anything else. But as it was pointed out, this does mean that atape that's just about ready to get marked full at, say, only 900 GB,might only report a little over 50% and then suddenly it's full. Thatcould cause some confusion.

We haven't been writing to the LTO-4s very long so I have no idea whatactual density we'll achieve. Maybe I'll wait until we have a number offull tapes and then take an average of all the amounts written and thenset the default to that values. Obviously, the more such tapes I havethe smaller my standard deviation about that mean value, and theseLTO-4s hold so much that it will be a while before I can run somereliable numbers.


George

Tim



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George Sinclair
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