ADSM-L

Re: Paul Zarnowski's comment

1995-03-08 11:36:34
Subject: Re: Paul Zarnowski's comment
From: Paul Zarnowski <VKM AT CORNELLC.CIT.CORNELL DOT EDU>
Date: Wed, 8 Mar 1995 11:36:34 EST
On Wed, 8 Mar 1995 08:30:29 PST Jacquelyn B. Reith said:
>Paul, in all the testing we have done over the years we had never
>seen the problem, so we do, indeed, think it is a rare problem.
>Our first attention went toward finding and fixing the problem.
>Now we will be developing a mechanism to determine which backup
>and archive files could be affected.
>
>Jacquie Reith
>ADSM Technical Support

Jacquie,

Thanks for the response.  I agree with your thinking that the first
priority should be to find and fix the problem.  I am always somewhat
uncomfortable using OCO (object code only) products, and since I cannot
look at the compression code myself to see what the problem might be,
I was hoping that you could provide us with a description of what the
problem was.  As you say, the first priority should be to fix the problem,
but it would be nice to get a description of it at some point.  Thanks.

I am also concerned about the following scenario:
Let's say a user backs their system up, and some files are truncated during
the backup, due to this compression problem.  Secondly, let's say that the
user restored the bad backup to their system, for whatever reason.

Q1: Would the restore of the truncated file fail, or would it simply restore
    the file incorrectly?

If the file is restored incorrectly, and the user does not become aware of
the bad file, it is likely that this bad file will now be backed up again
by ADSM during the next incremental backup.  Some days later, the remaining
inactive backups of this file will expire.  These remaining inactive backups
would be the only valid copies of this file at this point, and they will
be expired.

Q2: Will this second backup be considered a "good backup" or a "bad backup"
    by the analysis tool that you are going to provide to us to determine if
    we have been affected by the compression problem?

If the second backup is considered a "good backup" by the analysis tool,
then it seems to me that there will be no way to detect whether this problem
occurred or not, on any node which restored any files.

Q3: Is this analysis correct?

Q4: One last question:  In your announcement, you said that the fixes would
    be available on Friday, but I did not see an estimated date for the
    analysis tool.  Do you have an estimate?

Thanks for your help.
..Paul
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