{{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 (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)
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, the NFS export for the boot-image should be hosted on a two node cluster.
The architecture of a
diskless
A diskless node (or diskless workstation) is a workstation or personal computer without disk drives, which employs network booting to load its operating system from a server. (A computer may also be said to ''act as a diskless node'', if its disks ...
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 comp ...
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 (
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 Ope ...
Tru64 UNIX
Tru64 UNIX is a discontinued 64-bit UNIX operating system for the Alpha instruction set architecture (ISA), currently owned by Hewlett-Packard (HP). Previously, Tru64 UNIX was a product of Compaq, and before that, Digital Equipment Corporation ( ...
).
The
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...
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''