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Re: [virt-tools-list] Default use of caching on raw volumes



Could you try :

1. Share a folder from winxp
2. From another box start copying a large file to the winxp share
3. Observe loadavg on the kvm host

Both with default settings and cache=none

I was getting loadavg ~35 ( on a 2xXeon E5520 ) with the default setting and read/write speeds around 20Mb/s .
With cache=none the loadavg dropped to ~3 and the speeds increased to 40Mb/s.

The host is ubuntu 10.04.
The guest is ubuntu 10.04 with raw image as disk.


From: "Thomas Fjellstrom" <tfjellstrom shaw ca>
To: virt-tools-list redhat com
Sent: Friday, August 20, 2010 12:00:41 PM
Subject: Re: [virt-tools-list] Default use of caching on raw volumes

After seeing this thread I tried to see what would happen with a windows xp
guest using lvm+virtio and changing the cache option to none. Performance
drops about 10-20MB/s. Whatever the default is, I get an average of 55MB/s
read according to hd-tune. With cache=none I get more like 35-40MB/s.


--


Nikolai K. Bochev
System Administrator




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