rsync vs. rcp

Donovan Baarda abo at
Thu Feb 20 10:02:14 EST 2003

On Thu, 2003-02-20 at 08:53, va_public  wrote:
> --- In rsync at, Donovan Baarda <abo at m...> wrote:
> > On Thu, 2003-02-20 at 05:55, va_public  wrote:
> > 
> > RSYNC DOES NOT WORK WITH 1GB+ FILES... unless you have a 
> sufficiently
> > large block size. See the following;
> > 
> >
> OK. I read the thread. Pretty interesting design discussion on rsync 
> internals.
> Has any of it been implemented in 2.5.6? When is it planned to 
> implement it?
> So, bottom line, you are telling me, dont use rsync for my Oracle 
> database backups?
> Thats a bummer. Oracle database files are pretty sparse and, at a 
> block level, very few things change, so I was hoping that 
> using 'rsync' instead of 'rcp' to do my daily backups would be 
> IMMENSELY faster.

If you notice, the critical thing in the formula is the number of
_different_ bytes.... not really the whole file size. If you know less
than 100M of the file is different, then use the block size recommended
for a 100M file.

For oracle database files, you probably also want to use a block size
that is a multiple of whatever internal unit size oracle uses.

> As per the final messages on the thread, just increasing the csum 
> from 2 to 4 bytes seemed to miraculously solve the problem, right? So 
> why isnt this patch being included?

because it breaks backwards compatibility with older rsync versions...
it needs a protocol version change which is a bit trickier to introduce
without causing problems.

ABO: finger abo at for more info, including pgp key

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