On Mon, 2013-04-29 at 10:21 +0000, James Harper wrote:
If anyone has a few seconds spare, could you please run the following and post the results:
dd if=/dev/zero of=test.bin bs=512 count=128 oflag=sync
along with the kernel version and arch, filesystem, layers (lvm, md, etc), and underlying hardware?
When I do it on a bare 7200RPM sata disk on a modern server running xfs I get 10-15kbytes/second. I've repeated this on 3 other servers on different hardware with similar results, but when I do it on a ~10yo PC with ext3 I get around 500kbytes/second - 50x faster. I suspect it might be the kernel version (3.8 on new server, 2.6 on old pc) and the implementation of O_SYNC in older kernels wrt metadata but I don't have enough data points to form any conclusions...
Thanks
James
Hi James, andrew@linux-bczj:~> dd if=/dev/zero of=test.bin bs=512 count=128 oflag=sync 128+0 records in 128+0 records out 65536 bytes (66 kB) copied, 6.00686 s, 10.9 kB/s andrew@linux-bczj:~> uname -a Linux linux-bczj.site 3.7.10-1.1-desktop #1 SMP PREEMPT Thu Feb 28 15:06:29 UTC 2013 (82d3f21) x86_64 x86_64 x86_64 GNU/Linux AMD Phenom and a hardware list attached Andrew Greig