[Gluster-users] Kernal implementation FUD yet again (was Re: IO performance cut down when VM on Gluster)

[Joe Julian]

We will bring this up at the next board meeting and vote on it. John Mark will reply with the date of that next meeting. 

Until that time, this topic is dead.

DO post new topics to offer POSITIVE suggestions as to how it could be implemented, offer to contribute to that end, and provide proof of concepts. 

DO NOT hijack another support thread. If you do so you will be banned. 

Stephan von Krawczynski <skraw at ithnet.com> wrote:

>On Sun, 13 Jan 2013 07:11:14 -0800
>Joe Julian <joe at julianfamily.org> wrote:
>
>> On 01/13/2013 04:14 AM, glusterzhxue wrote:
>> > Hi all,
>> > We placed Virtual Machine Imame(based on kvm) on gluster file
>system, 
>> > but IO performance of the VM is only half of the bandwidth.
>> > If we mount it on a physical machine using the same volume as the 
>> > above VM, physical host reaches full bandwidth. We performed it
>many 
>> > times, but each had the same result.
>> What you're seeing is the difference between bandwidth and latency.
>When 
>> you're writing a big file to a VM filesystem, you're not performing
>the 
>> same operations as writing a file to a GlusterFS mount thus you're
>able 
>> to measure bandwidth. The filesystem within the VM is doing things
>like 
>> journaling, inode operations, etc. that you don't have to do when 
>> writing to the client requiring a lot more I/O operations per second,
>
>> thus amplifying the latency present in both your network and the
>context 
>> switching through FUSE.
>> 
>> You have two options:
>> 1. Mount the GlusterFS volume from within the VM and host the data 
>> you're operating on there. This avoids all the additional overhead of
>
>> managing a filesystem on top of FUSE.
>> 2. Try the 3.4 qa release and native GlusterFS support in the latest 
>> qemu-kvm.
>
>Thank you for telling the people openly that FUSE is a performance
>problem
>which could be solved by a kernel-based glusterfs.
>
>Do you want to make drivers for every application like qemu? How many
>burnt
>manpower will it take until the real solution is accepted?
>It is no solution to mess around _inside_ the VM for most people, you
>simply
>don't want _customers_ on your VM with a glusterfs mount. You want them
>to see
>a local fs only.
>
>-- 
>Regards,
>Stephan
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