Hello, apparently I have found an issue with btrfs: performance reduces with nodatasum and multi-device "raid0" or "single". I was testing with a series of 8 LIO ramdisks, with btrfs on those in multi-device single mode, and writing zeroes on the filesystem with 16 dd in parallel. Performance decreases significantly if the filesystem is mounted with nodatasum, or with nodatacow which implies nodatasum. CPU occupation also reduces, together with speed, as seen with htop. At first I thought it was my problem, but then I saw this web page http://www.linux-mag.com/id/7308/3/ which also reports reduced performance with nodatasum and multi-device raid0 or single, e.g. see these two lines: Btrfs two disks, single standard 50.144 50.264 126.984 131.130 Btrfs two disks, single nodatacow, nodatasum 43.834 47.603 131.612 131.470 similarly with raid0 even more with compression: Btrfs two disks, raid0 -o compress 70.234 69.048 130.852 129928 Btrfs two disks, raid0 -o compress nodatacow, nodatasum 48.762 48.831 130.812 130.202 If you go higher with the performances, such as with ramdisks, in the GB/sec range, it reduces more than that. I have noticed upto 50% reduction. It would be important to fix this problem for high-performance usages of btrfs. Best regards BM -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html