another point is, that a correct configured multipathing is way more solid when it comes to a single path outage. at the software side, i have seen countless nfs servers which where unresponsive because of lockd issues for example, and only a reboot fixed this since its kernel based. another contra for me is, that its rather complicated and a 50/50 chance that a nfs failover in a nfs ha setup works without any clients dying. dont get me wrong, nfs is great for small setups. its easy to setup, easy to scale, i use it very widespread for content sharing and homedirs. but i am healed regarding vm images on nfs. On Thu, Jan 9, 2014 at 8:48 AM, Karli Sjöberg <Karli.Sjoberg@slu.se> wrote:
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
On Jan 9, 2014 8:30 AM, "Karli Sjöberg" <Karli.Sjoberg@slu.se> wrote: On Thu, 2014-01-09 at 07:10 +0000, Markus Stockhausen wrote: > > Von: users-bounces@ovirt.org [users-bounces@ovirt.org]" im Auftrag von "squadra [squadra@gmail.com] > > Gesendet: Mittwoch, 8. Januar 2014 17:15 > > An: users@ovirt.org > > Betreff: Re: [Users] Experience with low cost NFS-Storage as VM-Storage? > > > > better go for iscsi or something else... i whould avoid nfs for vm hosting > > Freebsd10 delivers kernel iscsitarget now, which works great so far. or go with omnios to get comstar iscsi, which is a rocksolid solution > > > > Cheers, > > > > Juergen > > That is usually a matter of taste and the available environment. > The minimal differences in performance usually only show up > if you drive the storage to its limits. I guess you could help Sven > better if you had some hard facts why to favour ISCSI. > > Best regards. > > Markus
Only technical difference I can think of is the iSCSI-level load-balancing. With NFS you set up the network with LACP and let that load-balance for you (and you should probably do that with iSCSI as well but you don´t strictly have to). I think it has to do with a chance of trying to go beyond the capacity of 1 network interface at the same time, from one Host (higher bandwidth) that makes people try iSCSI instead of plain NFS. I have tried that but was never able to achieve that effect, so in our situation, there´s no difference. In comparing them both in benchmarks, there was no performance difference at all, at least for our storage systems that are based on FreeBSD.
/K
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