{{no footnotes, date=August 2016
A diskless shared-root cluster is a way to manage several machines at the same time. Instead of each having its own
operating system
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ...
(OS) on its local disk, there is only one image of the OS available on a server, and all the nodes use the same image. (SSI cluster =
single-system image
In distributed computing, a single system image (SSI) cluster is a cluster of machines that appears to be one single system. The concept is often considered synonymous with that of a distributed operating system, but a single image may be presente ...
)
The simplest way to achieve this is to use a NFS server, configured to host the generic boot image for the SSI cluster nodes. (pxe + dhcp + tftp + nfs)
To ensure that there is no
single point of failure
A single point of failure (SPOF) is a part of a system that would Cascading failure, stop the entire system from working if it were to fail. The term single point of failure implies that there is not a backup or redundant option that would enab ...
, the NFS export for the boot-image should be hosted on a two node cluster.
The architecture of a diskless
computer cluster
A computer cluster is a set of computers that work together so that they can be viewed as a single system. Unlike grid computers, computer clusters have each node set to perform the same task, controlled and scheduled by software. The newes ...
makes it possible to separate servers and storage array. The operating system as well as the actual reference data (userfiles, databases or websites) are stored competitively on the attached storage system in a centralized manner. Any server that acts as a cluster node can be easily exchanged by demand.
The additional abstraction layer between storage system and computing power eases the scale out of the infrastructure. Most notably the storage capacity, the computing power and the network bandwidth can be scaled independent from one another.
A similar technology can be found in
VMScluster
A VMScluster, originally known as a VAXcluster, is a computer cluster involving a group of computers running the OpenVMS operating system. Whereas tightly coupled multiprocessor systems run a single copy of the operating system, a VMScluster is l ...
(
OpenVMS
OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using Op ...
) and
TruCluster
TruCluster is a closed-source high-availability clustering solution for the Tru64 UNIX operating system. It was originally developed by Digital Equipment Corporation (DEC), but was transferred to Compaq in 1998 when Digital was acquired by the co ...
(
Tru64 UNIX
Tru64 UNIX is a discontinued 64-bit UNIX operating system for the DEC Alpha, Alpha instruction set architecture (ISA), currently owned by Hewlett-Packard (HP). Previously, Tru64 UNIX was a product of Compaq, and before that, Digital Equipment Corp ...
).
The
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...
implementation of a diskless shared-root cluster is known as Open-Sharedroot.
Literature
* Marc Grimme, Mark Hlawatschek, Thomas Merz ''Data sharing with a Red Hat GFS storage cluster''
* Marc Grimme, Mark Hlawatsche ''German Whitepaper: Der Diskless Shared-root Cluster'' (PDF-Datei; 1,1 MB)
* Kenneth W. Preslan ''Red Hat GFS 6.1 – Administrator’s Guide''