Re: Poor Windows performance on ceph RBD.

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hello

I did not do windows vm on kvm since years but back in time for good io
performance on windows vm on kvm virtio driver has to be installed.

https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/stable-virtio/virtio-win.iso

oau

Le jeudi 02 avril 2020 à 15:28 +0000, Frank Schilder a écrit :
> Dear all,
> 
> maybe someone can give me a pointer here. We are running OpenNebula
> with ceph RBD as a back-end store. We have a pool of spinning disks
> to create large low-demand data disks, mainly for backups and other
> cold storage. Everything is fine when using linux VMs. However,
> Windows VMs perform poorly, they are like a factor 20 slower than a
> similarly created linux VM.
> 
> If anyone has pointers what to look for, we would be very grateful.
> 
> The OpenNebula installation is more or less default. The current OS
> and libvirt versions we use are:
> 
> Centos 7.6 with stock kernel 3.10.0-1062.1.1.el7.x86_64
> libvirt-client.x86_64                      4.5.0-
> 23.el7_7.1            @updates 
> qemu-kvm-ev.x86_64                         10:2.12.0-
> 33.1.el7          @centos-qemu-ev
> 
> Some benchmark results from good to worse workloads:
> 
> rbd bench --io-size 4M --io-total 4G --io-pattern seq --io-type write
> --io-threads 16 : 450MB/s
> rbd bench --io-size 4M --io-total 4G --io-pattern seq --io-type write
> --io-threads 1  : 230MB/s
> rbd bench --io-size 1M --io-total 4G --io-pattern seq --io-type write
> --io-threads 1  : 190MB/s
> rbd bench --io-size 64K --io-total 4G --io-pattern seq --io-type
> write --io-threads 1  : 150MB/s
> rbd bench --io-size 64K --io-total 1G --io-pattern rand --io-type
> write --io-threads 1 : 26MB/s
> 
> dd with conv=fdatasync gives awesome 500MB/s inside linux VM for
> sequential write of 4GB.
> 
> We copied a couple of large ISO files inside the Windows VM and for
> the first ca. 1 to 1.5G it performs as expected. Thereafter, however,
> write speed drops rapidly to ca. 25MB/s and does not recover. It is
> almost as if Windows translates large sequential writes to small
> random writes.
> 
> If anyone has seen and solved this before, please let us know.
> 
> Thanks and best regards,
> 
> =================
> Frank Schilder
> AIT Risø Campus
> Bygning 109, rum S14
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