[ovirt-devel] [RFE] treat local NFS storage as localfs

[Pavel Gashev]

On Wed, 2016-12-21 at 16:25 +0100, Martin Sivak wrote:
> 
> So VMs on one host will get better IO performance and the others will
> still use NFS as they do now.

Performance is not an issue when all I/O bound VMs are co-located with
disks. If all VMs are I/O bound, all hosts in a cluster can use local
storage.

> It is an interesting idea, I am just not sure if having poor-man's
> hyperconverged setup with all the drawbacks of NFS is worth it.
> Imagine for example what happens when that storage provider host
> needs
> to be fenced or put into maintenance. The whole cluster would go down
> (all VMs would lose storage connection, not just the VMs from the
> affected host).

Losing a server together with a storage could be an issue, or not. It
really depends on setup. At least it would be good to provide such
feature :)

> I will let someone from the storage team to respond to this, but I do
> not think that trading performance (each host has its own local
> storage) and resilience (well, at least one failing host does not
> affect the others) for migrations is a good deal.
> 
> --
> Martin Sivak
> SLA / oVirt
> 
> On Wed, Dec 21, 2016 at 2:18 PM, Sven Kieske <s.kieske at mittwald.de>
> wrote:
> > 
> > On 21/12/16 11:44, Pavel Gashev wrote:
> > > 
> > > Hello,
> > > 
> > > I'd like to introduce a RFE that allows to use a local storage in
> > > multi
> > > server environments https://bugzilla.redhat.com/show_bug.cgi?id=1
> > > 406412
> > > 
> > > Most servers have a local storage. Some servers have very
> > > reliable
> > > storages with hardware RAID controllers and battery units.
> > > 
> > > Example user cases:
> > > https://www.mail-archive.com/users@ovirt.org/msg36719.html
> > > https://www.mail-archive.com/users@ovirt.org/msg36772.html
> > > 
> > > The best way to use local storage in multi server "shared"
> > > datacenters
> > > is exporting it over NFS. Using NFS allows to move disks and VMs
> > > among
> > > servers.
> > > 
> > > In order to improve performance, disk I/O bound VMs can be pinned
> > > to
> > > a host with local storage. However there still is a performance
> > > drawback of NFS layers. Treating a local NFS storage as a local
> > > storage
> > > improves performance for VMs pinned to host.
> > > 
> > > Currently setting up of NFS exports is out of scope of oVirt.
> > > However
> > > this would be a way to get rid of "Local/Shared" storage types of
> > > datacenter. So that all storages are shared, but local storages
> > > are
> > > used as local.
> > > 
> > > Any questions/comments are welcome.
> > > 
> > > Specifically I'd like to request for comment on potential data
> > > integrity issues during online VM or disk migration between NFS
> > > and
> > > localfs.
> > > 
> > 
> > Just let me say that I really like this as an end user.
> > 
> > Hope this get's in. This seems less overhead than a complete
> > hyperconverged gluster setup.
> > 
> > 
> > --
> > Mit freundlichen Grüßen / Regards
> > 
> > Sven Kieske
> > 
> > Systemadministrator
> > Mittwald CM Service GmbH & Co. KG
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> > 32339 Espelkamp
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> > F: +495772 293333
> > https://www.mittwald.de
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> > Oeynhausen
> > Komplementärin: Robert Meyer Verwaltungs GmbH, HRB 13260, AG Bad
> > Oeynhausen
> > 
> > 
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