On Tue, May 29, 2001 at 12:02:41PM -0500, Phil Howard wrote:
> Dave Dykstra wrote:
>
> > On Fri, May 25, 2001 at 02:19:59PM -0500, Dave Dykstra wrote:
> > ...
> > > Use the -W option to disable the rsync algorithm. We really ought to make
> > > that the default when both the source and destination are local.
> >
> > I went ahead and submitted a change to the rsync CVS to automatically turn
> > on -W when the source and destination are both on the local machine.
>
> So how do I revert that on the command line?
>
> I've been trying with -W doing my disk to disk backups, and I've had
> to go back to not using -W. Will -c do that?
There's currently no way to revert it. I thought it wouldn't be necessary,
and I'm not sure how to do it cleanly, because there's currently no precedent
in rsync for a general undoing of options that have different defaults
depending on the situation. Another one that comes to mind is --block-io.
The latest rsync in CVS is now using the "popt" package to process
options intead of getopt. Does anybody know if that package has a standard
way to negate options, for example prefixing a "no" (like --no-block-io) or
something like that? I took a quick look through the man page and it
wasn't obvious.
> The reason is the load
> on the machine gets so high, nothing else can run. This is not CPU
> load, but rather, buffering/swapping load. CPU load just slows other
> things down. But buffering/swapping load brings other things to a
> grinding halt. I suspect Linux's tendency to want to keep everything
> that anything writes in RAM, even if that means swapping out all other
> processes, is impacted by this. So I'll need a way to not have the
> effect of -W to use rsync for disk to disk backups.
Wow. Rsync is just going too fast for it I guess. The -W makes it do
a lot of unnecessary disk I/O which must be enough to throttle its
progress. Sure seems like leaving out -W is the wrong solution. Maybe
-W has to turn off more of rsync's pipelining since it is no longer
performing the rsync algorithm.
> The fact that rsync loads so much into VM probably makes the problem
> a bit worse in this case. I saw 1 process at 35M and 2 processes at
> 70M (total 175M used by rsync, in addition to all the buffered writes).
Does -W have an impact on that? I would think that if anything -W would
lessen that effect.
> I'm wondering if rsync is even a good choice for disk to disk backup
> duty. Is there some option I missed that disables pre-loading all
> the file names into memory?
Maybe it isn't. There is no such option.
> I also tried the --bwlimit option and it had no effect, not even on
> the usual download syncronizing over a dialup that I do. I could
> not get it to pace the rate below the dialup speed no matter what
> I would specify.
I haven't used the --bwlimit option and don't really know how it works.
I remember when somebody contributed it that I was skeptical about how
well it could work. I'm especially not surprised that it has no impact
on local-to-local transfers.
- Dave Dykstra
