On Fri, Nov 12, 2010 at 15:36, Joe Pruett <joey@q7.com> wrote: > i just did a bit of poking around and discovered that snapshots have > their own chunk size that is used for the copy on write magic. indeed. i was hoping someone would advise me if there was a better chunk size, which is why i said what i thought i was using (default = 64k) in my first post. > and it > defaults to 4k, and you can only increase that to 512k. a simple test > of creating a 1g file went from 240mbytes/sec to 4mbytes/sec with 4k > chunk, and 12mbytes/sec with 512k chunk. so i'm not sure what the > bottleneck is, but is surely is there. interestingly the default snapshot chunk size on my system: LVM version: 2.02.56(1)-RHEL5 (2010-04-22) Library version: 1.02.39-RHEL5 (2010-04-22) Driver version: 4.11.5 is 4k. a tutorial i was reading suggested it was 64k, and i didn't doublecheck if that was true. i am going to have to wait til after business hours to run more thorough tests, but i still see a slowdown way over 10x even at 64k chunk size with a single snapshot. i'll try it at all the different available chunk sizes and report back by monday. still curious about Zumastor--does anyone use this in production? _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
