High Performance Linux Clusters with OSCAR, Rocks, OpenMosix, and MPI [Electronic resources] نسخه متنی

2.5 CD-ROM-Based Clusters

If you just want to learn about
clusters, only need a cluster occasionally, or can't
permanently install a cluster, you might consider one of the
CD-ROM-based clusters. With these, you create a set of bootable
CD-ROMs, sometimes called "live
filesystem" CDs. When you need the cluster, you
reboot your available systems using the CD-ROMs, do a few
configuration tasks, and start using your cluster. The cluster
software is all available from the CD-ROM and the
computers' hard disks are unchanged. When you are
done, you simply remove the CD-ROM and reboot the system to return to
the operating system installed on the hard disk. Your cluster
persists until you reboot.

Clearly, this is not an approach to use for a high-availability or
mission-critical cluster, but it is a way to get started and learn
about clusters. It is a viable way to create a cluster for short-term
use. For example, if a computer lab is otherwise idle over the
weekend, you could do some serious calculations using this approach.

There are some significant difficulties with this approach, most
notably problems with storage. It is possible to work around this
problem by using a hybrid approachsetting up a dedicated
system for storage and using the CD-ROM-based systems as compute-only
nodes.

Several CD-ROM-based systems are available. You might look at
ClusterKnoppix,
http://bofh.be/clusterknoppix/,
or Bootable Cluster CD (BCCD), http://bccd.cs.uni.edu/. The next subsection,
a very brief description of BCCD, should give you the basic idea of
how these systems work.

2.5.1 BCCD

BCCD was developed by Paul Gray as
an educational tool. If you want to play around with a small cluster,
BCCD is a very straightforward way to get started. On an occasional
basis, it is a viable alternative. What follows is a general overview
of running BCCD for the first time.

The first step is to visit the BCCD download site, download an ISO
image for a CD-ROM, and use it to burn a CD-ROM for each system.
(Creating CD-ROMs from ISO images is briefly discussed in Chapter 4.) Next, boot each machine in your cluster
from the CD-ROM. You'll need to answer a few
questions as the system boots. First, you'll enter a
password for the default user, bccd. Next,
you'll answer some questions about your network. The
system should autodetect your network card. Then it will prompt you
for the appropriate driver. If you know the driver, select it from
the list BCCD displays. Otherwise, select
"auto" from the menu to have the
system load drivers until a match is found. If you have a DHCP and
DNS server available on your network, this will go much faster.
Otherwise, you'll need to enter the usual network
configuration informationIP address, netmask, gateway, etc.

Once the system boots, log in to complete the configuration process.
When prompted, start the BCCD heartbeat process. Next, run the
utilities
bccd-allowall
and
bccd-snarfhosts.
The first of these collects hosts' keys used by SSH
and the second creates the machines file used by
MPI. You are now ready to use the system.

Admittedly, this is a pretty brief description, but it should give
you some idea as to what's involved in using BCCD.
The boot process is described in greater detail at the
project's web site. To perform this on a regular
basis with a number of machines would be an annoying process. But for
a few machines on an occasional basis, it is very straightforward.