try it, i bet that you will get better latency results with proper configured iscsitarget/initiator. 

btw, freebsd 10 includes kernel based iscsi-target now. which works pretty good for me since some time, easy to setup and working performing well (zfs not to forget ;) )


On Thu, Jan 9, 2014 at 9:20 AM, Markus Stockhausen <stockhausen@collogia.de> wrote:
> Von: Karli Sjöberg [Karli.Sjoberg@slu.se]
> Gesendet: Donnerstag, 9. Januar 2014 08:48
> An: squadra@gmail.com
> Cc: users@ovirt.org; Markus Stockhausen
> Betreff: Re: [Users] Experience with low cost NFS-Storage as VM-Storage?
>
> On Thu, 2014-01-09 at 08:35 +0100, squadra wrote:
> Right, try multipathing with nfs :)
>
> Yes, that´s what I meant, maybe could have been more clear about that,
> sorry. Multipathing (and the load-balancing it brings) is what really
> separates iSCSI from NFS.
>
> What I´d be interested in knowing is at what breaking-point, not having
> multipathing becomes an issue. I mean, we might not have such a big
> VM-park, about 300-400 VMs. But so far running without multipathing
> using good ole' NFS and no performance issues this far. Would be good to
> know beforehand if we´re headed for a wall of some sorts, and about
> "when" we´ll hit it...
>
>/K

If that is really a concern for the initial question about a "low cost NFS
solution" LACP on the NFS filer side will mitigate the bottleneck from
too many hypervisors.

My personal headache is the I/O performance of QEMU. More details here:
http://lists.nongnu.org/archive/html/qemu-discuss/2013-12/msg00028.html
Or to make it short: Each I/O in a VM gets a penalty of 370us. That is much
more than in ESX environments.

I would be interested if this the same in ISCSI setups.

Markus



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