On Mon, Dec 21, 2015 at 8:14 AM, Hugo Mills <h...@carfax.org.uk> wrote: > On Sun, Dec 20, 2015 at 07:26:07PM -0600, Donald Pearson wrote: >> I read an implication in a different thread that defrag and autodefrag >> behave differently in that autodefrag is more snapshot friendly for >> COW data. >> >> Did I understand that correctly? I have not been doing defrag on my >> virtual machine image directory because I do use a snapshot schedule >> and the way I understood things, a defrag would basically decouple the >> live data from the snapshots and greatly increase utilization. >> >> It sounded like autodefrag does not have this problem? > > Correct.
Hum? How is that so? Snapshot-aware defrag was disabled almost 2 years ago, and that piece of code is used both by a "manual" defrag (ioctl) and by automatic defrag. > >> If that's true, is there any case where it would not be best practice >> to mount with autodefrag enabled? > > When you are already tight on I/O bandwidth for your application. > autodefrag increases the amount of I/O the disks do (because it's > rewriting parts of the file near each write, as well as just the piece > that's being written by userspace). > > Hugo. > > -- > Hugo Mills | UNIX: Japanese brand of food containers > hugo@... carfax.org.uk | > http://carfax.org.uk/ | > PGP: E2AB1DE4 | -- Filipe David Manana, "Reasonable men adapt themselves to the world. Unreasonable men adapt the world to themselves. That's why all progress depends on unreasonable men." -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
