[Lustre-discuss] How to start

[Daire Byrne]

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.

> 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'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.

> Also, I made different partitions in the servers for the MDT and OST.
> I *can* build the lustrefs using those partitions, can't I?

Yes you can use any device including partitions. You could also just use the 
raw unpartitioned devices (or software RAIDs, LVMs, DRDB).

> Node names are configured inside lustre, or are they just the domain
> names i set up in the computers?

They are taken from the hostnames. When setting up failover you need to supply
the failover hostname to the mkfs.lustre command.

> 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.

Daire