Hi,
What HV is that? CentOS? Are you using the right tuned profile? What about in the guest? Which
IO scheduler?
--
Sent from the Delta quadrant using Borg technology!
Nux!
www.nux.ro
----- Original Message -----
> From: "Ivan Kudryavtsev" <kudryavtsev_ia@bw-sw.com>
> To: "users" <users@cloudstack.apache.org>
> Sent: Friday, 17 May, 2019 10:13:50
> Subject: Poor NVMe Performance with KVM
> Hello, colleagues.
>
> Hope, someone could help me. I just deployed a new VM host with Intel P4500
> local storage NVMe drive.
>
> From Hypervisor host I can get expected performance, 200K RIOPS, 3GBs with
> FIO, write performance is also high as expected.
>
> I've created a new KVM VM Service offering with virtio-scsi controller
> (tried virtio as well) and VM is deployed. Now I try to benchmark it with
> FIO. Results are very strange:
>
> 1. Read/Write with large blocks (1M) shows expected performance (my limits
> are R=1000/W=500 MBs).
>
> 2. Write with direct=0 leads to expected 50K IOPS, while write with
> direct=1 leads to very moderate 2-3K IOPS.
>
> 3. Read with direct=0, direct=1 both lead to 3000 IOPS.
>
> During the benchmark I see VM IOWAIT=20%, while host IOWAIT is 0% which is
> strange.
>
> So, basically, from inside VM my NVMe works very slow when small IOPS are
> executed. From the host, it works great.
>
> I tried to mount the volume with NBD to /dev/nbd0 and benchmark. Read
> performance is nice. Maybe someone managed to use NVME with KVM with small
> IOPS?
>
> The filesystem is XFS, previously tried with EXT4 - results are the same.
>
> This is the part of VM XML definition generated by CloudStack:
>
> <devices>
> <emulator>/usr/bin/kvm-spice</emulator>
> <disk type='file' device='disk'>
> <driver name='qemu' type='qcow2' cache='none' discard='unmap'/>
> <source
> file='/var/lib/libvirt/images/6809dbd0-4a15-4014-9322-fe9010695934'/>
> <backingStore type='file' index='1'>
> <format type='raw'/>
> <source
> file='/var/lib/libvirt/images/ac43742c-3991-4be1-bff1-7617bf4fc6ef'/>
> <backingStore/>
> </backingStore>
> <target dev='sda' bus='scsi'/>
> <iotune>
> <read_bytes_sec>1048576000</read_bytes_sec>
> <write_bytes_sec>524288000</write_bytes_sec>
> <read_iops_sec>100000</read_iops_sec>
> <write_iops_sec>50000</write_iops_sec>
> </iotune>
> <serial>6809dbd04a1540149322</serial>
> <alias name='scsi0-0-0-0'/>
> <address type='drive' controller='0' bus='0' target='0' unit='0'/>
> </disk>
> <disk type='file' device='cdrom'>
> <driver name='qemu' type='raw'/>
> <backingStore/>
> <target dev='hdc' bus='ide'/>
> <readonly/>
> <alias name='ide0-1-0'/>
> <address type='drive' controller='0' bus='1' target='0' unit='0'/>
> </disk>
> <controller type='scsi' index='0' model='virtio-scsi'>
> <alias name='scsi0'/>
> <address type='pci' domain='0x0000' bus='0x00' slot='0x09'
> function='0x0'/>
> </controller>
>
> So, what I see now, is that it works slower than couple of two Samsung 960
> PRO which is extremely strange.
>
> Thanks in advance.
>
>
> --
> With best regards, Ivan Kudryavtsev
> Bitworks LLC
> Cell RU: +7-923-414-1515
> Cell USA: +1-201-257-1512
> WWW: http://bitworks.software/ <http://bw-sw.com/>
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