On Sat, 2009-10-17 at 12:13 -0700, Mike Connell wrote: > > Interesting. If you're not using incremental recursion (the default in > > rsync >= 3.0.0), I can see that the "du" would help by forcing the > > destination I/O to overlap the file-list building in time. But with > > incremental recursion, the "du" shouldn't be necessary because rsync > > actually overlaps the checking of destination files with the file-list > > building on the source. > > Ignoring incremental recursion for a moment.
Don't ignore it, it makes a difference. > It seems to me that anything > that can warm up the file cache before it is needed would be beneficial? I didn't reason it out carefully enough; let's try again... Warming up the destination file cache decreases the amount of time the generator spends blocked on I/O. So the answer is yes, provided that the generator is the bottleneck. If incremental recursion is not used, that's almost certainly the case during the main phase of the rsync run, since the generator is checking all the destination files but the sender is only processing the small number of source files that need a transfer. But with incremental recursion, the sender and generator are checking files in parallel, so the sender may be the bottleneck depending on the relative speeds or disk configurations of the machines. (I take it that your rsync run is local. For remote runs, the network could be the bottleneck.) -- Matt -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html