ADSM-L

Re: ANR13300E & ANR1331E

2005-11-02 13:29:31
Subject: Re: ANR13300E & ANR1331E
From: Neil Schofield <neil.schofield AT YORKSHIREWATER.CO DOT UK>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 2 Nov 2005 18:28:22 +0000
Richard

It's an interesting point you raise about CRC checking. I debated this
extensively with IBM support in the course of the PMR. The CRC checking on
storage pool data only gives you a way of checking for corruption after it
has occurred - eg through auditing volumes.

This would have left me no better off as auditing the volumes without CRC
data enabled showed the corruption anyway. The CRC checking would only have
made a difference if the meta data (ITSM frame data) was intact but the
user data (contents of bitfiles) was corrupt.

What I wanted was a way of detecting the corruption at the time it
occurred. I have received excellent explanations why this is not possible
from a TSM point of view if the OS or drive do not report an error. The
only alternative is to do a read-after-write, but this is prohibitive from
a performance point-of-view.

We've had nothing like it since, but I must say it shook my confidence for
a long while afterwards.

Regards
Neil Schofield
Yorkshire Water Services Ltd.



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