[GLLUG] KVM Performance

Ken Smith kens at kensnet.org
Wed Jun 10 14:37:02 UTC 2020

Mike Brodbelt via GLLUG wrote:
> On 09/06/2020 22:52, Ken Smith via GLLUG wrote:
>> I can' t help thinking that there must be something more behind a 
>> drop from 60MB/s to 15MB/s in write performance
> Can't speak to your exact bottleneck here, but I think I'd try and 
> eliminate your disk hardware from the game for a start, to see what 
> happens there.
> Try creating a null block device 
> (https://www.kernel.org/doc/html/latest/block/null_blk.html), and then 
> benchmark writes to that on the host and the guest. See what that does 
> as a baseline....
> Mike
Interesting - thanks for the tip. I measured 16.3 MB/s write to a null 
block device on one of the guests.

Conclusion - that's as fast as that hardware can manage.

:-) Ken

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