100% sure that the precomressed file will transfer in substantially less
time.
also consider that rsync will have to transfer and whole file, not just
parts of it. rsync transfers all files that have changed and it has to
transfer the whole file becuase rsync does not do any kind of 'diff' between
the files and only transfer changed parts, it transfers the whole file
always.
rsync only determines if a file has been changed or not, then either
transfers the whole file or doesnt.
rsync qualifies something as changed if a)filesize has changed b) last write
date has changed c) permissions have changed.
also, the ssh compression is a very simple binary compression. meaning, ssh
will compress sequential numbers of binary data such as
001000100010001000100010001000100010001000100010 would compress to something
like 6x00100010(yes, its over simplified!). the whole point of this
statement is to let you know that ssh doesnt have a library of compression
keys and doesnt compress very efficiently.(in terms of data size transfered,
it is great for compressing terminal data where their is a lot of null
characters on the screen!)
On 10/15/07, Adam Goryachev <[EMAIL PROTECTED]> wrote:
>
> >
> >> On 10/15/07, *Toni Van Remortel* <[EMAIL PROTECTED]
> >> <mailto:[EMAIL PROTECTED]>> wrote:
> >>
> >>
> >> So I like to change to dumping MySQL with mysqldump. Much cooler,
> >> but
> >> how to store those dumps? Should I store them compressed (gzip)
> >> or not?
> >> I do use compression in BackupPC through ssh (-C option).
> >>
> >> My main concern is bandwidth usage, not local filesystem space.
> >> So which
> >> option uses the least bandwidth?
> >>
> dan wrote:
> > if the concern is network bandwidth, compress the sql dump first so
> > backuppc transfers a compressed and theirfore smaller file accross the
> > network. that would use the least bandwidth. good luck :)
> >
> I suppose if your uncompressed file is 500M which compresses down to
> 200M, and assuming you are using rsync.
>
> How much data will rsync transfer (incl your ssh level compression)
> compared to the compressed version of the file? ie, I would assume more
> of the sections of the file will be identical in the uncompressed rather
> than the compressed file. Ultimately, if you can test this and let us
> know your results, that would be helpful for other people (like me :)
>
> Currently I compress the sql backups to save disk space on the sql
> server, but it would be interesting to note which is more efficient
> bandwidth wise....
>
> Regards,
> Adam
>
>
>
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