[ovirt-users] Best Storage Option: iSCSI/NFS/GlusterFS?

[Charles Tassell]

Hi Marcin,

   Hmm, so if you are using multipath with VDSM you have to manually 
edit the vdsm.conf file to put the right IP in every time the active 
controller switches?  That sort of defeats the purpose of multipath....  
That was the issue we were having: we'd spin up another host, it would 
connect to the SAN which would then reballance the disks among 
controllers, and all our other hosts would lose their connection to the 
active controller and pause all of the VMs.  It's the "Device is not on 
preferred path" issue that is common on the MD3x00 line.  We had the 
same errors with VMWare, but VMWare was able to automatically switch to 
the active path.

On 2017-03-26 05:42 PM, Marcin Kruk wrote:
> But on the Dell MD32x00 you have got two controllers. The trick is 
> that you have to sustain link to both controllers, so the best option 
> is to use multipath as Yaniv said. Otherwise you get an error 
> notifications from the array.
> The problem is with iSCSI target.
> After server reboot, VDSM tries to connect to target which was 
> previously set, but it could be inactive.
> So in that case you have to remember to edit configuration in 
> vdsm.conf, because vdsm.conf do not accept target with multi IP addresses.
>
> 2017-03-26 9:40 GMT+02:00 Yaniv Kaul <ykaul at redhat.com 
> <mailto:ykaul at redhat.com>>:
>
>
>
>     On Sat, Mar 25, 2017 at 9:20 AM, Charles Tassell
>     <ctassell at gmail.com <mailto:ctassell at gmail.com>> wrote:
>
>         Hi Everyone,
>
>           I'm about to setup an oVirt cluster with two hosts hitting a
>         Linux storage server.  Since the Linux box can provide the
>         storage in pretty much any form, I'm wondering which option is
>         "best." Our primary focus is on reliability, with performance
>         being a close second.  Since we will only be using a single
>         storage server I was thinking NFS would probably beat out
>         GlusterFS, and that NFSv4 would be a better choice than
>         NFSv3.  I had assumed that that iSCSI would be better
>         performance wise, but from what I'm seeing online that might
>         not be the case.
>
>
>     NFS 4.2 is better than NFS 3 in the sense that you'll get DISCARD
>     support, which is nice.
>     Gluster probably requires 3 servers.
>     In most cases, I don't think people see the difference in
>     performance between NFS and iSCSI. The theory is that block
>     storage is faster, but in practice, most don't get to those limits
>     where it matters really.
>
>
>           Our servers will be using a 1G network backbone for regular
>         traffic and a dedicated 10G backbone with LACP for redundancy
>         and extra bandwidth for storage traffic if that makes a
>         difference.
>
>
>     LCAP many times (especially on NFS) does not provide extra
>     bandwidth, as the (single) NFS connection tends to be sticky to a
>     single physical link.
>     It's one of the reasons I personally prefer iSCSI with multipathing.
>
>
>           I'll probably try to do some performance benchmarks with 2-3
>         options, but the reliability issue is a little harder to test
>         for.  Has anyone had any particularly bad experiences with a
>         particular storage option?  We have been using iSCSI with a
>         Dell MD3x00 SAN and have run into a bunch of issues with the
>         multipath setup, but that won't be a problem with the new SAN
>         since it's only got a single controller interface.
>
>
>     A single controller is not very reliable. If reliability is your
>     primary concern, I suggest ensuring there is no single point of
>     failure - or at least you are aware of all of them (does the
>     storage server have redundant power supply? to two power sources?
>     Of course in some scenarios it's an overkill and perhaps not
>     practical, but you should be aware of your weak spots).
>
>     I'd stick with what you are most comfortable managing - creating,
>     backing up, extending, verifying health, etc.
>     Y.
>
>
>
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