On Sun, Jan 4, 2009 at 11:24 AM, Avi Kivity <avi@redhat.com> wrote:
quoted text
> Alexander Atticus wrote:
>>
>> Hello!
>>
>> I have been experimenting with KVM and have been experiencing poor write
>> I/O
>> performance.  I'm not sure whether I'm doing something wrong or if this is
>> just the current state of things.
>>
>> While writing to the local array on the node running the guests I get
>> about
>> 200MB/s from dd (bs=1M count=1000) or about 90MB/s write performance from
>> iozone (sequencial) when I write to a 2G file with a 16M record length.
>>  The
>> node is an 8 disk system using 3ware in a RAID50 configuration.  It has
>> 8GB
>> of RAM.
>>
>> The guests get much slower disk access. The guests are using file based
>> backends (tried both qcow2 and raw) with virtio support.  With no other
>> activity on the machine, I get about 6 to 7MB/s write performance from
>> iozone with the same test. Guests are running Debian lenny/sid with
>> 2.6.26-1-686.
>>
>
> qcow2 will surely lead to miserable performance.  raw files are better.
>  best is to use lvm.
>

What do you mean with best is to use lvm ?
You just say to use raw images on an lvm partition because you can
easily resize it ? Or somehow images only use the used space of the
raw file when used with lvm ? Or there's some trick to make it ?





Thanks a lot,

Rodrigo
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html