Open Stack

Alvise,


On 28 November 2013 08:44, Alvise Dorigo <alvise.dorigo at pd.infn.it> wrote:

> My requirements are:
>  - extendability (new disk array transparently added without any outage)
>  - high performance on big files (glance and nova usually manage big files)
>  - POSIX / mount as a normal filesystem with unique naming space
>  - easy to install/manage (and supported on RHEL 6.x)
>
> Any advice or report on your experience would be very appreciated.
>

You may be including this as part of the "easy to install/manage" part, but
I'd strongly recommend adding "hitless upgrades" to that list.
This isn't so much an issue with older systems like NFS, but newer systems
like Gluster and Ceph are moving forward at a tremendous rate.  When the
time comes to do an upgrade you are probably not going to want to have to
remove the whole shared storage in order to do it.

I'm still working on my Openstack cluster, but I have a bit of experience
in other environments with Gluster and NFS.  It is non-trivial to do NFS
without a single point of failure but apart from that it is very well
documented, well understood and mature.  Gluster is completely fault
tolerant but I have seen issues with the self-healing it does where virtual
machines will be locked from writing to their virtual disks for over 2
minutes at a time.  Upgrades to Gluster can be scary, and if you make use
of replication then it is non-trivial to ensure that the appropriate
replication pairs are formed especially following a failure (for example,
if you have 2 racks of machines then you might want all the bricks from
rack 1 to be replicated to servers in rack 2.)  You can get full support
from RedHat for Gluster which may be an advantage over other FSs.

Regards,
Dan
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