On 09/10/2012 09:33 PM, Daniel Tschritter wrote: > Hi everybody, > > I got a server with CentOS 6.3 and KVM as a host and a windows 2k8 > guest. > > The windows machine's disk performance is very poor. > The windows guest uses VirtIO disk drivers, no cache and uses a LVM > partition on a Raid1. > > atop shows 100% disk utilization as soon as the windows guest accesses > the HDD, data transfers figures given are most times less than 1MB/s > r/w, peaks are around 3MB/s r/w. > > I've run a few tests to see what's going on: > > Creating a 10GB test file on CentOS (guests switched off): > time dd if=/dev/random of=testfile bs=1 count=0 seek=10G > 0+0 records in > 0+0 records out > 0 bytes (0 B) copied, 5.777e-06 s, 0.0 kB/s > real 0m0.001s > user 0m0.000s > sys 0m0.000s > > Create copy of test file created above: > time cp testfile testfile2 > real 0m3.136s > user 0m0.440s > sys 0m2.693s > That looks ok to me. According to atop data transfer rates are between > 130 and 180MB/s. > > Create copy of test file above while Windows guest boots up: > time cp testfile testfile2 > real 0m3.367s > user 0m0.515s > sys 0m2.826s > not much different... > > Creating copy of test file above within the Win2k8R2 guest: > Current Time: 20:12:32,41 > copy testfile testfile2 > 1 file(s) copied > Current Time: 20:22:08,64 > 576,23s > That takes about 170 time longer than the copy unter CentOS! > > I've run the same test on a CentOS6.3 guest with the following results: > time cp testfile testfile2 > real 0m3.950s > user 0m0.470s > sys 0m3.383s > that's almost as quick as the host... > > I've run these tests a few times, always giving about the same result. > > Why is the disk performance in the Win guest that poor? > > What can be done to improve things? Your tests are invalid. On Linux the files you create are sparse, on Windows they are not. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
