Tomasz Chmielewski wrote: > Is it possible (planned?) to make rsync avoid going through system cache > and use direct IO? > > Right now, if you decide to backup your desktop system (but it's not > only about desktop systems; rather more about one-time-only data > transfers) to external disk, you will notice that your X session lags > terribly, mainly because: > > - system caches everything what rsync reads from the original drive, > - system caches everything what rsync writes to the destination drive, > - while doing the above, current cache is being empties. > > > I've seen some discussions on rsync mailing list in the past about such > a feature (avoiding using system cache), but I'm not sure if there were > any conclusions out of it.
The details of how to use O_DIRECT are quite non-portable. Even on a single OS, the details vary between different filesystem types and different kernel versions. In theory, there are posix_madvise() or madvise() flags to accomplish the goal described above, but how well they work varies a lot. But at least those functions, especially posix_madvise(), should be portable enough to use as an option in rsync. -- Jamie -- 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
