Re: cpu usage for GTAR on alpha

[Joerg Schilling]

>From: Uncle George <address@hidden>

>224 min 'the program top' time. which is cpu time. the 78% to 90% ( with
>it appearing every 5 secs ~82% in RN state, rather than in the expected
>D ( disk activity ) state! ).

>The program AMANDA, a backup system, would like to estimate disk usage.
>it does this by running the backup program, in this case "tar", and
>dumping all data to /dev/null. Amanda appears to expect that each drive
>should take no longer that 5min to scan. 

>"running: /bin/gtar: /bin/gtar --create --file /dev/null --directory /
>--one-file-system --listed-incremental
>/usr/local/var/amanda/gnutar-lists/mylaptop__0.new --sparse
>--ignore-failed-read --totals . "

>anyway, doing some further tests, i have used the 'time find .' command
>to just go through the directories. for a file count of 443k, wall time
>is some 47min, with 8sec user, 23sec system time.

If you have sparse files in the gigabyte range, GNUtar is really slow.

In general, you can never expect that you may scan a filesystem with many 
sparse files and no OS support for sparse file backup in less than 5 minutes.

Also note that GNUtar is very very slow with scanning sparse files.

Try star from ftp://ftp.fokus.gmd.de/pub/unix/star/alpha/

the latest release is 4x faster than GNUtar with sparse files.

Jörg

 EMail:address@hidden (home) Jörg Schilling D-13353 Berlin
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