Tag Archives: high availability

Computer cluster

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Computer cluster – Wikipedia, the free encyclopedia.

A computer cluster is a group of linked computers, working together closely thus in many respects forming a single computer. The components of a cluster are commonly, but not always, connected to each other through fast local area networks. Clusters are usually deployed to improve performance and availability over that of a single computer, while typically being much more cost-effective than single computers of comparable speed or availability.[1]

And now I will put together clusters for high availability and load balancing.  This is where VMs come in handy.   I think I  prefer loosely coupled clusters, clusters where individual nodes are separated on different power grids.

It’s always nice to have a succinct definition handy to stay focused.

The Linux Virtual Server Project – Linux Server Cluster for Load Balancing

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What is the Linux Virtual Server?

The Linux Virtual Server is a highly scalable and highly available server built on a cluster of real servers, with the load balancer running on the Linux operating system. The architecture of the server cluster is fully transparent to end users, and the users interact as if it were a single high-performance virtual server. For more information, click here.

The Linux Virtual Server Project – Linux Server Cluster for Load Balancing.

How to hot-swap SATA drives in Linux

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If you want the drives to be automounted and your automount system uses pmount to do the mounting (pmount allows mounting by a normal user without an entry in /etc/fstab) you may need to edit /etc/pmount.allow. If the drives are seen as non-removable, which SATA hard disks usually are, pmount will refuse to mount them unless you add the device name to /etc/pmount.allow, for example.

echo ‘/dev/sdb1’ >>/etc/pmount.allow

echo ‘/dev/sdc[123]’ >>/etc/pmount.allow

echo ‘/dev/sdd*’ >>/etc/pmount.allow

The first allows one particular partition to be mounted by pmount, the second example permits three specific partitions on a drive, while the third lets through every partition on a drive. Note the use of single quotes to stop the shell interpreting the wildcards.

via How to hot-swap SATA drives in Linux | TuxRadar Linux.

ClusterLabs

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Pacemaker keeps your applications running when they or the machines they’re running on fail. However it can’t do this without connectivity to the other machines in the cluster – a significant problem in its own right.

Rather than re-implement the wheel, Pacemaker supports existing implimentations such as Heartbeat. Heartbeat provides:

  • a mechansigm to reliably send messages between nodes,
  • notifications when machines appear and disappear
  • a list of machines that are up that is consistent throughout the cluster

Heartbeat was also the first stack supported by the Pacemaker codebase.

via FAQ – ClusterLabs.

Linux Server Cluster for Load Balancing

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The Linux Virtual Server is a highly scalable and highly available server built on a cluster of real servers, with the load balancer running on the Linux operating system. The architecture of the server cluster is fully transparent to end users, and the users interact as if it were a single high-performance virtual server. For more information, click here.

via The Linux Virtual Server Project – Linux Server Cluster for Load Balancing.