Hi, last year I built a server with 3 SATA disks. I used a physical volume for each disk, a volume group on each, and then created identical LVs in each VG. Then I used dmesetup to create a RAID 0 over all 3 disks. A single disk has an I/O performance of 70 MB/s. After creating a filesystem on the RAID and measuring its performance I got the expected result: 210 MB/s. But this setup was too complicated for me, so I tried a different approach. Still a physical volume for each disk (actually partiton 2 which is nearly the complete disk), but only one volume group vg0. The commands used were: pvcreate /dev/sda2 pvcreate /dev/sdb2 pvcreate /dev/sdc2 vgcreate vg0 -s 128 /dev/sda2 /dev/sdb2 /dev/sdc2 On vg0, I created a LV which should span all 3 disks and therefore be equivalent to a RAID 0: lvcreate --name=test -L 10000M -i 3 vg0 Resulting LV: --- Logical volume --- LV Name /dev/vg0/ubuntu VG Name vg0 LV Write Access read/write LV Status available # open 1 LV Size 10,12 GB Current LE 81 Segments 1 Allocation inherit Read ahead sectors 0 Block device 254:10 However, I get only half the expected performance. I created an XFS filesystem and mounted it on /mnt/tmp: # dd if=/dev/zero of=/mnt/tmp/bla bs=1024k count=10000 10485760000 Bytes (10 GB) kopiert, 112,233 Sekunden, 93,4 MB/s # dd if=/mnt/tmp/bla of=/dev/null bs=1024k count=10000 10485760000 Bytes (10 GB) kopiert, 88,8886 Sekunden, 118 MB/s This was measured with kernel 2.6.23.12 and 2.6.25.1 on AMD64 X2. Is it possible to get 210 MB/s? Thanks, hjb -- Pro-Linux - Germany's largest volunteer Linux support site http://www.pro-linux.de/ Public Key ID 0x3DDBDDEA
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