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List:       lustre-discuss
Subject:    [Lustre-discuss] Some questions about Lustre FS and building SAN.
From:       mahashmi () gmail ! com (Mustafa A !  Hashmi)
Date:       2006-12-15 0:42:38
Message-ID: 5f636a2f0612142342j57b30135q6aa2e3445fdd4241 () mail ! gmail ! com
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On 12/15/06, Nathaniel Rutman <nathan@clusterfs.com> wrote:
> Igor Zhbanov wrote:
> >
> > Second, I want to build system consisting of several frontend-nodes
> > and two-four backend (storage) nodes. I don't want to use hardware shared
> > storage for some reasons. So, I can use some networking block device
> > to connect two nodes (e.g. DRBD v0.8 in primary/primary mode) if needed.

Discussed earlier in a thread as well. DRBD in primary/primary mode
isn't required and won't work given Lustre's design. Something like
GFS can make use of this, however, that doesn't work beyond a two node
configuration. Even using gndb to export drives to other systems and
creating layer upon layer to construct redundant shared storage gets
complicated far too quickly. Using LVM mirroring is an option,
however, that's a discussion for the relevant mailing list.

> > The question, is it possible to setup Lustre in such configuration:
> > 1) over DRBD or local hard drives if possible on two or four storage
> > nodes;

> We have heard of some success using network block devices, although
> your performance will probably be bad.

We're running such an implementation and also moving towards medium
sized deployments for client sites. Some deployments are already in
place and waiting to enter a production environment.

There is obviously the overhead of DRBD which comes into play if one
wants to run an active/active failover for storage, however, quite a
bit is dependent on the network, deployment scenario, client base,
etc.

The point is: it works quite well and integrates with HA services for
failover as is most often required.

> > 2) to be able mount Lustre file system at frontend nodes which have no
> > direct access to shared storage device, i.g. is it possible to mount
> > Lustre over network?;
> That's the whole point of Lustre.  Clients just need network connections
> to the servers.
> > 3) to have failover and load-balancing storage nodes, so each node
> > will hold entire copy of stored data, so storage nodes can be accessed
> > in parallel and if one node goes down, system will function correctly.
> >
> To do this you need a true shared storage device, because you need
> access to
> the data if either node goes down - a device network-shared from a down
> node does no good.  Lustre does not currently provide a RAID-type of data
> backup, although there are future plans to do this.

Again, this is where DRBD comes in if using local storage. Works
splendidly well.
-- 
Mustafa A. Hashmi
mahashmi@gmail.com

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