[Linux-cluster] Home-brew SAN/iSCSI

[Ray Van Dolson]

On Sat, Oct 10, 2009 at 12:21:29PM -0700, Madison Kelly wrote:
> Mike Cardwell wrote:
> > Madison Kelly wrote:
> > 
> >>   Until now, I've been building 2-node clusters using DRBD+LVM for the 
> >> shared storage. I've been teaching myself clustering, so I don't have 
> >> a world of capital to sink into hardware at the moment. I would like 
> >> to start getting some experience with 3+ nodes using a central SAN disk.
> >>
> >>   So I've been pricing out the minimal hardware for a four-node 
> >> cluster and have something to start with. My current hiccup though is 
> >> the SAN side. I've searched around, but have not been able to get a 
> >> clear answer.
> >>
> >>   Is it possible to build a host machine (CentOS/Debian) to have a 
> >> simple MD device and make it available to the cluster nodes as an 
> >> iSCSI/SAN device? Being a learning exercise, I am not too worried 
> >> about speed or redundancy (beyond testing failure types and recovery).
> > 
> > Yeah, that's possible. Just use iscsid to export the device. If this is 
> > just for testing/learning purposes have you considered using virtual 
> > machines to minimise the hardware footprint? You could have a single 
> > host machine that acts as the SAN, exporting a device using iscsid and 
> > three vm's running on top of VMWare server on the same machine which 
> > make up the cluster...
> 
> Thanks! I was thinking that was what I could do, but I wanted to ask 
> before sinking a lot of time/money just to find out I was wrong. :)
> 
> I thought about Xen VMs. I'll have to see if I can simulate things like 
> fence devices and such. Though, as good as virtualization is, I wonder 
> how close I could get to simulating real world? When I run into 
> problems, it would be another layer to wonder about. However, there is 
> no denying the cost savings! I will look into that more.

Another option, at least with VMware, would be to create a shared disk
that can be seen by all your VM's.

A bit simpler than setting up iSCSI, though that would be a good thing
to learn in it of itself...

Ray