Kirk
We will carry forward between releases all the Sources (detections),
but we are not going to carry between releases all versions of all
objects (objects = star or galaxy in deep/coadded catalog). So in
practice, if you base your publication on Object table from DR 2,
and we have on disk DR 3 and 4, in order to reproduce your results
you will need to stage data from DR2.
Another use case: students/astronomers who want to stay with
a given release and do their analysis on a relatively small data
sample for an extended period of time.
The answer might be that whoever wants to get data from old
releases need to find a space at his local institute and stage it
there, I don't know. I do know we need to take care of this issue.
Hmm, let's talk about it tomorrow.
Jacek
Kirk Borne wrote:
I guess I am not clear on what would be contained in the older releases.
In some (most?) projects, the newer releases supercede (and
include) the contents of the older releases. I suppose the
older releases do include unique calibrated data products
that were calibrated under some prior version of the data
processing/calibration algoriths. In that case, I can see
some utility and value in having the older releases available.
However, having these releases instantly accessible on spinning
disks (versus archival backup media) is another issue.
- Kirk
Date: Tue, 11 Jul 2006 15:56:10 -0700
From: Jacek Becla <[EMAIL PROTECTED]>
Subject: [LSST-data] disk space for old releases
To: LSST Data Management <[email protected]>
Keywords: DataAccWG
Hello,
In our current disk storage estimates we are assuming we will need
disk space for 2 most recent releases and unreleased catalog.
But what about the disk space for older releases that some people might
want to stage in from tape? That is not included in the estimates.
How much should we reserve for that? Equivalent of size of the most
recent release?
BTW, if we end up being limited by disk IO and not space, we will
get that "space for free" anyway, BUT... it is important to get
an idea how much disk space we will need because disk io pushes us
towards smaller disks (which are faster, have better seek time),
so we can end up in a situation where required number of
small disks does not give us enough disk space (I went through
the numbers with Don and that can happen). I'm in the process
of building a model for that.
Jacek
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