On Jul 3, 2008, at 4:07 PM, Evren Yurtesen wrote:
> Renke Brausse wrote:
>> Hello Tony,
>>> I've written before about backups involving very big files that
>>> seem to execute slowly.
>>>
>>> What can be slowing things down so much? Except for this
>>> operation, everything else runs about as I would expect.
>> I have no clue what the reason is but I experienced that backups of
>> large files are much faster with tar over ssh instead of rsync
>> over ssh.
>> Not an explanation but maybe this can solve your problem.
>
> I believe the reason for this is how rsync works. It normally tries
> to transfer only the changed parts of the file. This is to save
> bandwidth, to do this, it has to scan the whole file on both sides
> (I guess). This is unnecessary unless you are over slow links. You
> might want to try the whole-file option with rsync:
>
> -W, --whole-file copy files whole (w/o delta-
> xfer algorithm)
>
> Please let us know the results, as a side-note if you still want to
> shrink the transferred file size you can use the ssh compression
> with -C option of ssh.
>
> Thanks,
> Evren
Reporting back on this. Using the -W option did not make much
difference. The dumps in question continue to run for a long time and
eventually fail with an ALARM.
For the time being I am excluding the really large files in question.
I may try tar instead of rsync at some point as was suggested.
Tony Schreiner
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