Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Mon, 23 Jul 2012 17:52:21 +0200 Phil Stricker wrote: > Hi! > > I just started with a setup of DRBD and Xenserver 6.0.2 > > Of course, my read-performance inside the VMs is very bad. Of course why? Did you expect a bad read performance and if so, what made you believe so? >The storage > system is a Raid 10 with 8x Intel 320 SSD on an LSI-Raid-Controller. > What LSI controller? I can get better performance than your 477MB/s with a software RAID 10 and just 5 plain 2TB Hitachi SATA drives... What is the speed of the raw backing device? For reads, it should be same as the DRBD device... > Testing the Read-Performance with hdparm on Dom-0 shows: > > /dev/drbd1: > Timing buffered disk reads: 1432 MB in 3.00 seconds = 477.18 MB/sec > You should be able to get much better numbers than that, also depending on your controller a RAID6 using 8 disks can be faster (in all aspects!) than a RAID 10 with 8 drives. Simply put, more active data disks to read from and write to. Of course the controller needs to have a fast enough CPU to do the checksum crunching. > HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate > ioctl for device > > If I start the same test in a VM, I get: > Timing buffered disk reads: 100 MB in 2.56 seconds = 39.10 MB/sec > > > There is just one single VM on that system. > > > Can you help me? Windows VMs have shown the same issue. That clearly looks like some Xen deficiency or configuration issue, can't help you with that, sorry. > The problem does > also consist, if the second node is disconnected... > Reads are ALWAYS local and should not be affected by the presence of replication or not. Regards, Christian -- Christian Balzer Network/Systems Engineer chibi at gol.com Global OnLine Japan/Fusion Communications http://www.gol.com/