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Re: Quiet tarring



On Tue, Oct 24, 2000 at 03:41:33PM +0900, Karen Ellrick wrote:
| At the moment the needs have changed, as all my
| users screamed that they didn't want the performance of the server brought
| to its knees once an hour to tar the files (the day they complained the
| loudest, the company president was on a trip and hadn't gotten his mail for
| a few days, and his mail spool file was growing to 40 or 50 MB - tarring
| that every hour was getting to be really noticable on our ancient hardware,
| and of course highly redundant).  I noticed that in your script, you used
| "&" to put the tar operation in the background - I should have done that to
| help with performance.

It won't help performance in the slightest. Why would it? The same work
must still be done - you're only affecting the timing, and probably
increasing the load since you're now letting other things happen while
the tar runs, which will slow up everything if your hardware is already
overburdened (which it sounds like it may be) - these things have a
knee curve: for a while adding parallelism is a win because the system
can run job B when job A blocks, resulting in better use of things but
past a certain point the cost of juggling the jobs exceeds the gain in
utilisation and beyond that things get no better,for a while and then
rapidly very much worse as you try even more things at once.

While on the topic, look at rsync. It does a damn fast incremental mode
(passes checksums instead of data across the wire) for files which
grow, like logs and mail. If your backup can be a directory tree
elsewhere instead of a tar file it can do wonders.

Cheers,
-- 
Cameron Simpson, DoD#743        cs zip com au    http://www.zip.com.au/~cs/

The national budget must be balanced. The public debt must be reduced; the
arrogance of the authorities must be moderated and controlled. Payments to
foreign governments must be reduced, if the nation doesn't want to go
bankrupt. People must again learn to work, instead of living on public
assistance.	- Marcus Tullius Cicero, 55 BC





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