KVM Bad disk performance

General support questions
henriqueps
Posts: 9
Joined: 2017/02/13 13:00:11

KVM Bad disk performance

Post by henriqueps » 2017/02/13 13:06:05

Hello folks.
We're having some troubles with kvm guest performance, and we would somebody could help us.
Actually we are testing KVM running on CentOS 7, with Windows guest and MSSQL installed.
The point is, this guest can't even reach 50% of the Vmware guest performance (the configurations are the same, same host, memory, disk, ...)
We're using LVM for storage for guest and to performance testing we're using HammerDB.

Here are my host configuration (is only for testing proposes):
Dell Poweredge 1950
Disk: 2 x 500GB Sata
Processor: 2 x Intel E5410
Memory: 32GB

Guest configuration
Processor: 8 (host-passthrough)
Memory: 30GB (it was not installed ballon driver)
Disk: 100GB (storaged on LVM volume and with Virtio blk driver)
Network: Installed with Virtio net driver

There is something that we are missing?
Could you please give us some light?

thermobee
Posts: 23
Joined: 2017/02/07 02:36:28

Re: KVM Bad disk performance

Post by thermobee » 2017/02/13 20:08:39

How do you define disk performance?

hunter86_bg
Posts: 2019
Joined: 2015/02/17 15:14:33
Location: Bulgaria
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Re: KVM Bad disk performance

Post by hunter86_bg » 2017/02/13 21:34:21

Check if the virtio-win rpm package is latest and the drivers installed in Win respectively.As far as I understood you , a host's Logical Volume was provided to the guest - is that right ? What is the sequential write/read speed of the guest?

henriqueps
Posts: 9
Joined: 2017/02/13 13:00:11

Re: KVM Bad disk performance

Post by henriqueps » 2017/02/14 14:00:03

thermobee wrote:How do you define disk performance?
We're using HammerDB to test performance.
I'll share with you a gsheet, where contain the performance charts. I think is better than I try to describe all here.

https://docs.google.com/spreadsheets/d/ ... sp=sharing

henriqueps
Posts: 9
Joined: 2017/02/13 13:00:11

Re: KVM Bad disk performance

Post by henriqueps » 2017/02/14 14:07:52

hunter86_bg wrote:Check if the virtio-win rpm package is latest and the drivers installed in Win respectively.As far as I understood you , a host's Logical Volume was provided to the guest - is that right ? What is the sequential write/read speed of the guest?
Yes the virtio is already in stable version, 0.1.126.
Yes, the LVM is to provide to the guest.

I'm using CristalDiskMark:
KVM Guest
Sequential write: 110MB/s
Sequential read: 132MB/s
VMware Guest
Sequential write: 100MB/s
Sequential read: 116MB/s

hunter86_bg
Posts: 2019
Joined: 2015/02/17 15:14:33
Location: Bulgaria
Contact:

Re: KVM Bad disk performance

Post by hunter86_bg » 2017/02/14 20:30:12

The strange thing is that KVM has better sequential speed, but fails to perform in acceptable rate.
Please provide the VM's configuration for the KVM machine. I'm interested in the disk section - the one starting with "<disk type=" and ending in "</disk>".The configuration files are located in /etc/libvirt/qemu folder by default.

henriqueps
Posts: 9
Joined: 2017/02/13 13:00:11

Re: KVM Bad disk performance

Post by henriqueps » 2017/02/14 23:00:45

hunter86_bg wrote:The strange thing is that KVM has better sequential speed, but fails to perform in acceptable rate.
Please provide the VM's configuration for the KVM machine. I'm interested in the disk section - the one starting with "<disk type=" and ending in "</disk>".The configuration files are located in /etc/libvirt/qemu folder by default.
Yes, this is very strange.
Here is the disk config:

<disk type='block' device='disk'>
<driver name='qemu' type='raw' cache='none' io='native'/>
<source dev='/dev/lvma4/win2k8r2'/>
<target dev='vda' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</disk>
<disk type='block' device='disk'>
<driver name='qemu' type='raw' cache='none' io='native'/>
<source dev='/dev/lvma4/win2k8r2-2'/>
<target dev='vdb' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
</disk>
<disk type='block' device='disk'>
<driver name='qemu' type='raw' cache='none' io='native'/>
<source dev='/dev/lvmb1/win2k8r2-1'/>
<target dev='vdc' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
</disk>

hunter86_bg
Posts: 2019
Joined: 2015/02/17 15:14:33
Location: Bulgaria
Contact:

Re: KVM Bad disk performance

Post by hunter86_bg » 2017/02/19 20:42:24

Everything seems OK to me.
As a sidenote , why are you testing a VM with a database solution , when DBs work best at baremetal ?

henriqueps
Posts: 9
Joined: 2017/02/13 13:00:11

Re: KVM Bad disk performance

Post by henriqueps » 2017/02/20 13:43:32

hunter86_bg wrote:Everything seems OK to me.
As a sidenote , why are you testing a VM with a database solution , when DBs work best at baremetal ?
In this way we could share our hardware with others instances.

cgokan
Posts: 34
Joined: 2016/12/07 13:11:56

Re: KVM Bad disk performance

Post by cgokan » 2017/02/20 15:17:44

KVM is not Windows performance. It would be better if you use an SSD disk. It is best to use Linux as much as possible.

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