ADSM-L

Re: Linux Sparse Files

2006-10-03 10:43:56
Subject: Re: Linux Sparse Files
From: Richard Sims <rbs AT BU DOT EDU>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Tue, 3 Oct 2006 10:42:19 -0400
Brian -

You'll have to examine the scheduler log and possibly the
dsmerror.log to determine why the backup was "unsuccessful".

My cumulative notes on sparse file handling in ADSM QuickFacts may be
helpful.  Whereas Unix systems have sparse files, but no file system
attributes to so flag them as such, any application has to plow
through the entire contents of the file to discern that it really is
sparse.  Though the physical file (as reportable by 'du -sk') may be
small, Unix generates the full entirety of the file's address range
when read, inserting nulls to represent the unused space.  This can
tax an application, and in TSM's case may lead to a timeout in
waiting for the application, depending upon conditions.  To make
matters worse, some of these files log system activity, and so can be
in continual flux, and so costly retries can be futile.  You should
consider excluding bogies like this one from backup.

   Richard Sims

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