Hello, Can anyone tell me why virtual disk performance on an lvm local sr running on mdadm raid 1 should be very slow? Please see test results below. System 1 XCP 1.6 running on mdadm raid1 fdisk -l output ---------------------------------------------- Disk /dev/sda: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sda1 * 1 13 104391 83 Linux /dev/sda2 14 654 5148832+ fd Linux raid autodetect /dev/sda3 655 13690 104711670 fd Linux raid autodetect Disk /dev/sdb: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 * 1 13 104391 83 Linux /dev/sdb2 14 654 5148832+ fd Linux raid autodetect /dev/sdb3 655 13690 104711670 fd Linux raid autodetect Disk /dev/md0: 5272 MB, 5272305664 bytes 2 heads, 4 sectors/track, 1287184 cylinders Units = cylinders of 8 * 512 = 4096 bytes Disk /dev/md0 doesn''t contain a valid partition table Disk /dev/md1: 107.2 GB, 107224629248 bytes 2 heads, 4 sectors/track, 26177888 cylinders Units = cylinders of 8 * 512 = 4096 bytes Disk /dev/md1 doesn''t contain a valid partition table ------------------------------------------------- sda1 and sdb1 are both 100M boot partitions XCP running on /dev/md0 (sda2 + sdb2 raid1) LVM SR on /dev/md1 (sda3 + sdb3 raid1) Benchmarks are run using dd bs=1M count=512 if=/dev/zero of=test conv=fdatasync Benchmark 1 run in / (xcp system root) = 53.1 MB/s Benchmark 2 run in /sbb/test (10G logical volume on Local Storage formatted ext3 and mounted on /sbb/test = 94.1 MB/s Benchmark 3 run in root of centos 5 fully paravirtualised vm on local storage = 31.5 MB/s -------------------------------------------------- System 2 Single disk (USING ONE OF THE ABOVE DISKS) FRESH STANDARD INSTALLATION OF XCP 1.6 WITH LVM LOCAL STORAGE Standard GPT partitioning When the above benchmarks are run on this system the results are as follows: Benchmark 1 run in / (xcp system root) = 89.5 MB/s Benchmark 2 run in /sbb/test (10G logical volume on Local Storage formatted ext3 and mounted on /sbb/test = 92.0 MB/s Benchmark 3 run in root of centos 5 fully paravirtualised vm on local storage = 61.0 MB/s (Same vm as above imported from xva file) ------------------------------------------------------------------------ ------------------------------------ My questions are: 1. Why is benchmark 1 slower on mdadm raid 1? 2 Why is benchmark 3 slower on mdadm raid 1? Yet benchmark 2 results are roughly the same. Am I missing something here and is it possible to tweak the performance of XCP on raid? Regards, Frank.