[Gluster-users] SAN vs. NAS Conundrum

[Paul Robert Marino]

On Mon, Nov 11, 2013 at 10:49 AM, Ellison, Bob <bob.ellison at ccur.com> wrote:
> Hello,
>
> I’m very new to GlusterFS and would like to see if it may fit into a storage
> solution I’m working on.
>
>
>
> I have a dual server system with 95TB of data (10 x 9.5TB GFS2 partitions;
> each partition being a 10+2 RAID6 under the covers) connected via Fibre
> Channel. So each server can see all the data and provide server failover
> (turn one server off, the other server picks up the load).  To complicate
> matters, there will be a need to expand this system to 190TB’s in about a
> year (20 x 9.5TB).
>
>
>
> A new customer requirement came in where I need to provide access to these
> partitions as an NFS NAS and the existing files in the 10 GFS2 partitions
> need to be presented as one very large 95TB file system. The client is
> unaware there is any server side directory hierarchy. All the client will do
> is read from the root of the 95GB partition and write new files to the root
> where the server must transparently write the file data to one of the 10
> GFS2 partitions in some distributed fashion (e.g. round-robin).
>
>
>
> GlusterFS provides the exact functionality I’m looking for - NAS + a union
> file system with a distributed write capability. However I get the idea that
> just laying GlusterFS on the existing system will probably not work. I’m
> mixing a SAN with a NAS and it seems that GlusterFS only can handle server
> level fault tolerance through data replication and that it cannot deal with
> the server level fault tolerance offered by the existing SAN. Data
> replication is not an option as the customer will not pay for twice the
> storage.
>
>
>
> So…
>
> - Can GlusterFS even work with GFS2 partitions or must it be XFS / EXT4 /
> (et al)?

In theory sure but you wouldn't want it to.
Under the hood XFS and GFS2 are very similar so what works well on one
will generally work well on the other.
Gluster normally handles its own replication so the idea of putting it
on a shared filesystem is not all that useful

>
>
>
> - Can GlusterFS be configured in to accommodate the existing SAN?

Not in your current configuration but it can very effectively be used
as a NAS head for redundant SANS

>
>
>
> - Even if I reconfigure such that these are XFS partitions and configure 5
> arrays on one server and 5 on the other and without replication, I believe a
> server failover would make the storage on the failed server inaccessible. Is
> this correct?

That is essentially correct. there is a possible way to get it to work
in an active passive mode but its a messy kludge so I wont get into
it.

In the scenarios you described simple NFS would probably be your best
bet. NFS 4 would be best but NFS 3 will work too  as long as the lock
file is also on a shared volume.then you could use Keepalived or
Parana  as a loadbalancer any you are done.


>
>
>
> Thanks very much,
>
>
>
> Bob Ellison
>
>
>
>
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