On Wed, Jul 17, 2013 at 06:04:48PM +0200, Valerio Pachera wrote: > 2013/7/17 Liu Yuan <namei.unix at gmail.com>: > > may you try it on you host too？oflag=sync is always slow. try oflag=direct > > instead > > Right, it was directsync...thank you. > > root at backup:/mnt/backup# dd if=/dev/zero of=c3 bs=1M count=1024 oflag=direct > 536870912 byte (537 MB) copiati, 6,81561 s, 78,8 MB/s > root at backup:/mnt/backup# dd if=/dev/zero of=c3 bs=1M count=1024 oflag=direct > 1073741824 byte (1,1 GB) copiati, 10,9185 s, 98,3 MB/s > root at backup:/mnt/backup# dd if=/dev/zero of=c4 bs=1M count=2048 oflag=direct > 2147483648 byte (2,1 GB) copiati, 35,2077 s, 61,0 MB/s > root at backup:/mnt/backup# sync > root at backup:/mnt/backup# dd if=/dev/zero of=c5 bs=1M count=4096 oflag=direct > 4294967296 byte (4,3 GB) copiati, 78,7128 s, 54,6 MB/s > root at backup:/mnt/backup# sync > root at backup:/mnt/backup# dd if=/dev/zero of=c6 bs=1M count=6144 oflag=direct > 6442450944 byte (6,4 GB) copiati, 115,853 s, 55,6 MB/s > was this on guest? I think you can try 'sheep -w directio,xxx ...' since you use ssd for cache. This is what I get from my laptop, with cache on SSD root at vm1:/mnt# dd if=/dev/zero of=test bs=1M count=2000 oflag=direct 2000+0 records in 2000+0 records out 2097152000 bytes (2.1 GB) copied, 8.0809 s, 260 MB/s sheep cache option: ' -w size=10000,directio,dir=/tmp/cache0' qemu '-drive if=virtio,cache=writeback' My SSD is Sandisk(128G) and less powerful than your 840 pro. So I think you should get higher throughput. Thanks Yuan |