Monday, 2 August 2010

Splendid Isolation

I wandered lonely as a.... typical - I come back from a week's leave with a post on cloud computing to discover that every cloud related title has already been used.

The last few weeks have seen what can only be called a storm of cloud activity - the release of the Openstack cloud software; Amazon adding a cloud tuned for High Peformance Computing applications to their collection; the publishing of two reports on academic use of clouds and, or course, the public launch of the NGS's own prototype cloud service.

Some commentators have claimed the launch of the Amazon service means that The Grid is Dead. Obviously, those of us in the grid world disagree - as Craig Lee of the Open Science Grid explains.

Alternatively, we are now all officially zombies - mmm.. brains.

People who see the cloud as a computional grid with all the nasty authentication stuff ripped out are misunderstanding the point of nasty authentication stuff in a world where not all data is open and access control and audit trains are vital.

The people who say that the cloud is the greatest thing since sliced bread are also missing the point. Most clouds are quick-and-easy ways to get your hands on a virtual machine. It is virtual machines that are the greatest thing since sliced bread.

Why? It is all about keeping things separate.

Many modern applications are bad neighbours. They do not sit happily on a server but need plumbing into web service containers such as Tomcat or Glassfish and databases such as MySQL or PostgreSQL. It is not uncommon for the applications to require specific versions of their supporting software.

Trying to persuade two such applications to co-exist on the same server is the stuff of system administrators nightmares - sitting on the sysadmin scale of horror somewhere near an operating system upgrade or running out of coffee.

Virtual Machines let you dump these applications and their hangers on in an isolated environment comparatively cheaply and easily. Isolating applications isn't a new idea - it was implemented in the mainframe systems of the 1960s - and system admins have been using techniques such as chroot jails for decades to provide some level of separation.

With apologies for borrowing great poetry to make a cheap point: Wordsworth's poem Daffodils - the one that starts 'I wandered lonely as a cloud' - mentions the 'the bliss of solitude'. It is the solutude of computing clouds that makes them useful.

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