[fedora-virt] Virt Disk Performance

[Ken Smith]

Richard W.M. Jones wrote:
> {snip}
> In general the best performance is going to be when you use a host LV
> (or partition) and avoid files.  In the guest you should enable
> virtio.  And for best performance make sure you are using the most
> recent qemu and kernel since a lot of work last year went into
> improving virtio.
>
> Here are some numbers from my laptop (consumer SATA drive) which has
> had not really any tuning or attention to performance.  The numbers
> are from the command:
>
>    dd if=/dev/zero of=<output>  bs=8k count=131072 conv=fsync
>
>    Host (F17) write to LV:                               59.5 MB/s
>    Guest (F16, virtio) write to file on ext4 filesystem: 37.4 MB/s
>
>
>> I've pulled most of the information you requested. See above. I
>> don't see any specific cache settings on either machine. Is there
>> somewhere I would see the default setting on the machine?
>>
> I'm out of the loop on what the default caching policy is these days.
> Hopefully libvirt is at least choosing a safe one.
>
>
>> The raw
>> files are the full size of the filesystem they are intended to hold.
>>
> Does this mean they're not sparse?
>
> Rich.
>
>
Thank you Richard. That has given me some pointers.

Ken

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