[Lustre-discuss] How to start

[Rayentray Tappa]

On Wed, 2009-03-04 at 11:09 +0000, Daire Byrne wrote:
> Rayentray,
> 
> ----- "Rayentray Tappa" <rtappa.ascentio at gmail.com> wrote:
> 
> > Hi List,
> > I'm working for a small government organization in South America, and
> > in our quest for a large distributed storage solution we ran across
> > Lustre.
> > We have some servers in which we're trying to build a prototype to
> > decide whether or not Lustre meets our requirements. 
> > Because of some hardware issues we've temporarily chosen RHEL5 as our
> > OS but will also give Debian a try later (so I might bug you later on
> > building Lustre from sources, but that will be another era).
> 
> It is personal choice but I find RHEL5 makes a very good Lustre server 
> distrobition and is far easier to maintain Lustre updates on.
> 

Thanks for the information, it's good to know we should have little
trouble maintaining this :)

> > Right now we are trying to build a Lustre filesystem with 4 servers:
> > 2 of them as MDS/MDT configured for failover, and the other two as OSS
> > with one and two OST respectively.
> 
> For testing you may want to simplify the setup and not bother with MDT 
> failover. Failover is really only useful for the case where there is a 
> hardware failure. Using STONITH to reboot crashed servers is usually 
> sufficient for most small installations.
> 

I'm testing this in order to build a large system later, where high
availability of the data store is a must - so we do want to check how
this works, what involves to configure it and what may happen in case of
failure and how to restore it. 

If it can be configured in a later stage, i.e. after having already
tested Lustre itself, it might be a good idea to learn only a few things
at the time :)

> > I've already installed the patched kernel, lustre-modules,
> > lustre-ldiskfs, lustre itself and the e2fsprog lustre provides. I've
> > also  added the lnet module to modprobe.conf.
> > So, now I guess I should start setting up my two MDS+MDT servers, and
> > here is were I'm stuck: the lustre manual and Mount Conf say
> > something about making a filesystem, showing how to proceed with MDT and OST.
> > But I don't understand how I'm supposed to set up the MDS and OSS later
> > :-/
> 
> Basically you format the partitions with "mkfs.lustre" and then you mount them
> with "mount -t lustre /dev/blah /mnt/blah". When mounting for the first time
> they communicate with the MGS (config server) and create the required configs
> automatically.
> 

Right :) I was informed yesterday that mds and oss are not actually
configuired but created whenever i create the mdt or ost. It makes more
sense now :)

> > What do you call "sites"? (I quote from Mount Conf: "There should be
> > one MGS per site, not one MGS per filesystem")
> 
> In this context site means "organisation/company". The MGS holds the configuration
> for all Lustre filesystem in an organisation. You only need one. If you are testing
> or only plan on having a single filesystem then it makes sense to colocate the MGS 
> and MDS on the same server/device. When you use mkfs.lustre on the MDT there is an
> option to make it the MGS too.
> 

Our idea is to have a main Lustre running, which will be replicated in
other two buildings. We still don't know how we will handle the
replication, maybe Lustre1.8 is already out then and we can use that, or
maybe we handle it with a separate unit of software that we need to
develop anyway with other purposes[1]. Does it make sense to have only
one MGS in that configuration?

[1] How easy/difficult is to become involved with Lustre development? I
want to propose to the organization that, given we need replication and
Lustre intends to provide it in version 2.0, we may help with its
development. How much work would that be? (rough idea). Anyone I can
contact specifically about this?

Thanks,


--
ra