Hallo Rainer, On Tue, Mar 17, 2020 at 02:04:22PM +0100, Rainer Krienke wrote: > Hello, > > I run a pve 6.1-7 cluster with 5 nodes that is attached (via 10Gb > Network) to a ceph nautilus cluster with 9 ceph nodes and 144 magnetic > disks. The pool with rbd images for disk storage is erasure coded with a > 4+2 profile. > > I ran some performance tests since I noticed that there seems to be a > strange limit to the disk read/write rate on a single VM even if the > physical machine hosting the VM as well as cluster is in total capable > of doing much more. > > So what I did was to run a bonnie++ as well as a dd read/write test > first in parallel on 10 VMs, then on 5 VMs and at last on a single one. > > A value of "75" for "bo++rd" in the first line below means that each of > the 10 bonnie++-processes running on 10 different proxmox VMs in > parallel reported in average over all the results a value of > 75MBytes/sec for "block read". The ceph-values are the peaks measured by > ceph itself during the test run (all rd/wr values in MBytes/sec): > > VM-count: bo++rd: bo++wr: ceph(rd/wr): dd-rd: dd-wr: ceph(rd/wr): > 10 75 42 540/485 55 58 698/711 > 5 90 62 310/338 47 80 248/421 > 1 108 114 111/120 130 145 337/165 > > > What I find a little strange is that running many VMs doing IO in > parallel I reach a write rate of about 485-711 MBytes/sec. However when > running a single VM the maximum is at 120-165 MBytes/sec. Since the > whole networking is based on a 10GB infrastructure and an iperf test > between a VM and a ceph node reported nearby 10Gb I would expect a > higher rate for the single VM. Even if I run a test with 5 VMs on *one* > physical host (values not shown above), the results are not far behind > the values for 5 VMs on 5 hosts shown above. So the single host seems > not to be the limiting factor, but the VM itself is limiting IO. > > What rates do you find on your proxmox/ceph cluster for single VMs? > Does any one have any explanation for this rather big difference or > perhaps an idea what to try in order to get higher IO-rates from a > single VM? > > Thank you very much in advance > Rainer As Eneko said, single thread vs multiple threads. How are you VMs configured (qm config <vmid>)?
> > > > --------------------------------------------- > Here are the more detailed test results for anyone interested: > > Using bonnie++: > 10 VMs (two on each of the 5 hosts) VMs: 4GB RAM, BTRFS, cd /root; > bonnie++ -u root > Average for each VM: > block write: ~42MByte/sec, block read: ~75MByte/sec > ceph: total peak: 485MByte/sec write, 540MByte/sec read > > 5 VMs (one on each of the 5 hosts) 4GB RAM, BTRFS, cd /root; bonnie++ -u > root > Average for each VM: > block write: ~62MByte/sec, block read: ~90MByte/sec > ceph: total peak: 338MByte/sec write, 310MByte/sec read > > 1 VM 4GB RAM, BTRFS, cd /root; bonnie++ -u root > Average for VM: > block write: ~114 MByte/sec, block read: ~108MByte/sec > ceph: total peak: 120 MByte/sec write, 111MByte/sec read How did you configure bonnie? And a CoW filesystem on top of Ceph will certainly drop performance. > > > Using dd: > 10 VMs (two on each of the 5 hosts) VMs: 4GB RAM, write on a ceph based > vm-disk "sdb" (rbd) > write: dd if=/dev/zero of=/dev/sdb bs=nnn count=kkk conv=fsync > status=progress > read: dd of=/dev/null if=/dev/sdb bs=nnn count=kkk status=progress > Average for each VM: > bs=1024k count=12000: dd write: ~58MByte/sec, dd read: ~48MByte/sec > bs=4096k count=3000: dd write: ~59MByte/sec, dd read: ~55MByte/sec > ceph: total peak: 711MByte/sec write, 698 MByte/sec read > > 5 VMs (two on each of the 5 hosts) VMs: 4GB RAM, write on a ceph based > vm-disk "sdb" (rbd) > write: dd if=/dev/zero of=/dev/sdb bs=4096k count=3000 conv=fsync > status=progress > read: dd of=/dev/null if=/dev/sdb bs=4096k count=3000 status=progress > Average for each VM: > bs=4096 count=3000: dd write: ~80 MByte/sec, dd read: ~47MByte/sec > ceph: total peak: 421MByte/sec write, 248 MByte/sec read > > 1 VM: 4GB RAM, write on a ceph based vm-disk "sdb" (rbd-device) > write: dd if=/dev/zero of=/dev/sdb bs=4096k count=3000 conv=fsync > status=progress > read: dd of=/dev/null if=/dev/sdb bs=4096k count=3000 status=progress > Average for each VM: > bs=4096k count=3000: dd write: ~145 MByte/sec, dd read: ~130 MByte/sec > ceph: total peak: 165 MByte/sec write, 337 MByte/sec read dd is not well suited for performance benchmarking. Better use bonnie++ or FIO. The later is good for storage benchmarks in general. As you now have the results from the top-most layer. How do the lower layers perform? Eg. FIO has a build-in rbd engine and is able to talk directly to an rbd image. For Ceph pool performance a rados bench can sure shed some light. -- Cheers, Alwin _______________________________________________ pve-user mailing list pve-user@pve.proxmox.com https://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-user
