<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi David,<div><br></div><div>1. Yes. That's the only disk in the system.</div><div><br></div><div>2. Yes:</div><div>nova1:/var/lib/nova/instances$ dd if=/dev/zero of=test bs=1M count=256<br>256+0 records in<br>256+0 records out<br>268435456 bytes (268 MB) copied, 2.04146 s, 131 MB/s<br><br></div><div>4. I have tried with:</div><div>- Linux Ubuntu 10.10</div><div>- FreeBSD 8.2 with virtio driver</div><div>- Windows 2008 R2 Server with virtio driver</div><div><br></div><div>3. my libvirt.xml </div><div><domain type='kvm'><br> <name>instance-00000121</name><br> <memory>1048576</memory><br> <os><br> <type>hvm</type><br> <boot dev="hd" /><br> </os><br> <features><br> <acpi/><br> </features><br> <vcpu>2</vcpu><br> <devices><br> <disk type='file'><br> <driver type='raw'/><br> <source file='/var/lib/nova/instances/instance-00000121/disk'/><br> <target dev='vda' bus='virtio'/><br> </disk><br> <disk type='file'><br> <driver type='raw'/><br> <source file='/var/lib/nova/instances/instance-00000121/disk.local'/><br> <target dev='vdb' bus='virtio'/><br> </disk><br><br> <interface type='bridge'><br> <source bridge='br100'/><br> <mac address='02:16:3e:33:42:e3'/><br> <filterref filter="nova-instance-instance-00000121-02163e3342e3"><br> <parameter name="IP" value="10.0.0.34" /><br> <parameter name="DHCPSERVER" value="10.0.0.9" /><br> </filterref><br> </interface><br><br> <!-- The order is significant here. File must be defined first --><br> <serial type="file"><br> <source path='/var/lib/nova/instances/instance-00000121/console.log'/><br> <target port='1'/><br> </serial><br><br> <console type='pty' tty='/dev/pts/2'><br> <source path='/dev/pts/2'/><br> <target port='0'/><br> </console><br><br> <serial type='pty'><br> <source path='/dev/pts/2'/><br> <target port='0'/><br> </serial><br><br> <graphics type='vnc' port='-1' autoport='yes' keymap='en-us' listen='0.0.0.0'/><br> </devices><br></domain><br><br></div><div><br><div>
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Met vriendelijke groet,<br><br>Martin van Wilderen<br>Technical Manager</div></div></div>
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<br><div><div>On Mar 26, 2012, at 4:45 PM, David Busby wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Hi Martin<div><br></div><div><ol><li>Does /var/lib/nova/instances reside on your SSD? (just double checking it's not instead pointing to a normal stoage device).</li><li>Do you see the expected performance on the host operating system?</li>
<li>Could you please provide the complete libvirt .xml file?</li><li>Could you please provide the operating system and version of the guest?</li></ol><div><br></div><div>Cheers</div><div><br></div><div>David</div><div><br>
</div><div><br></div><br><div class="gmail_quote">On Mon, Mar 26, 2012 at 1:59 PM, Martin van Wilderen - JDN BV <span dir="ltr"><<a href="mailto:martin@jdn.nl">martin@jdn.nl</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi List,<br>
<br>
I have a question about KVM disk performance. We are using Openstack Nova on three machines. These machines have a SSD drive with a dd write performance of about 130mb/s<br>
<br>
Within the instance the write performance is down to about 5 mb/s. When using the allocate trick (dd zero to disk before newfs) we get a performance of 20 mb/s.<br>
<br>
Things a have tried but don't give any extra results are:<br>
- Settings the disklayout from qcow2 to raw<br>
- Settings the cache type in libvirt.xml (writeback, writethrough, none)<br>
- Switching KSM on and off.<br>
- Tested with different guests OS, Linux, FreeBSD, Windows.<br>
<br>
Is there someone who had some extra info i can check? Or are there more people with this issue?<br>
<br>
Snippet from libvirt.xml<br>
<driver type='qcow2'/ cache='writeback'/><br>
<source file='/var/lib/nova/instances/instance-00000113/disk'/><br>
<target dev='vda' bus='virtio'/><br>
<br>
Kind regards,<br>
<br>
Martin<br>
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