What is Cloud Computing?

May 12, 2012

Someone from the non-technical business side asked me what is this Cloud computing all about. If you search for the term you find a bunch of definitions and descriptions. For example, on Wikipedia:

“Cloud computing refers to the delivery of computing and storage capacity as a service to a heterogeneous community of end-recipients.”
http://en.wikipedia.org/wiki/Cloud_computing.

That doesn’t sound like anything new. We had similar things even in the sixties. You have to read more of the above article to see the differences. But, to see what it really means a blog post, “Startups are Creating a New System of the World for IT“, puts it in context.


Hierarchical Storage Management, from drive to cloud

January 7, 2012

Years ago I came upon the HSM concept. Is this now applicable in today’s networked world for personal use? I propose HSM can be extended to encompass the Cloud.

HSM is an enterprise data storage technique, a tiered storage. Data is automatically moved from expensive but fast storage systems like hard disk arrays to cheaper but slower systems like optical or tape drive.

Conceptually, HSM is analogous to the cache found in most computer CPUs, where small amounts of expensive SRAM memory running at very high speeds is used to store frequently used data, but the least recently used data is evicted to the slower but much larger main DRAM memory when new data has to be loaded. — http://en.wikipedia.org/wiki/Hierarchical_storage_management

In the consumer world we have in our PCs fast hard drives and on mobile devices fast flash memory. A simple two tiered system would migrate least recently used files from local media to the cloud. In the home or SOHO environment, a three-tiered system is possible. Solid-State Drives (SSD) of modest size could be the 1st tier, SATA disk the 2nd, and finally, Cloud services can provide the 3rd tier.

For example, you have a PDF on your system that is a great resource, but you haven’t used it in a few weeks. The HSM manager would take that file and move it to the cloud (secure, private, encrypted, …., of course). In its place, to allow access by the user, is a link to the HSM managed storage location. Next time you use the file it will be migrated back to the local storage (but now also backed up in the cloud).

This is really an application of “file virtualization“.

Note that the HSM in enterprise systems is not simply based on “files” but on the underlying storage mumbo jumbo (frames, and all that).

This approach could make the potential future Windows 8 ‘Storage Spaces’ be even more useful. On *nix OS this is possible to implement now. It probably already is.

Demo
Here is a conceptual demo. We’ll use a known cloud storage service provider like Dropbox. As far as I know, Dropbox does not offer HSM.

On your PC you set a property on various folders that makes them eligible for HSM monitoring. This could be accomplished using a GUI and drag&drop. The HSM will immediately copy the folders to the SSD on your system or the main hard drive, if the files are not already on the fastest subsystem. In the original location of the folders, a link to the new locations will be created (soft links?). The end user will not see any difference. Kind of like “web folders” or WebDAV protocol.

After a period of time, the local HSM monitor will record which files have not been used and invoke the Dropbox local service to stream the files to the cloud. All that remains on the file system are links to the remote files; storage space is reclaimed.

Updates
Feb 26, 2012: Another company will be competing with DropBox. As above it allows the user to designate specific folders to participate in cloud storage. Since remote files will be slower to access, this company will attempt to “predict” which files would be used more often. See this article.

Further Reading


Bob Dylan “With god on our side”


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