What’s wrong with Storage Virtualization 1.0?

ORIGINALLY POSTED 30th November 2007

12,255 views on developerworks

I can’t help it. It seems that every post that Mr Yoshida makes strikes me as being somewhat questionable. I have much respect for how long he has been in the blogging game. I have no respect for his lack of reader comment acceptance – I’ve long since given up replying as he decides to ignore those that he doesn’t like – maybe they make too much sense…

Anyway, I see over in Hu’s World he’s trying to suggest that Hitachi are ahead of the game releasing their version 2 of USP earlier this year, the USP-V, and calling it “Virtualization 2.0” – trying to jump on the Web 2.0 bandwagon suggesting that this brings the mobility of data and business continuance – but also a subtle dig in his ‘labeling’ by dropping the SAN based, to controller based.

Its worth noting that SVC v1.1.0, released back in 2003, the first SVC release contained online data migration. Exactly what Hu describes in terms of a 2.0 enabler. That is, the ability to migrate data online without disruption. Its a fundamental of Storage Virtualization. Nothing new here, still Virtualization 1.0. As for business continuance, replication, again this has been available in SVC since the first release in 2003.

My main gripe, yet again, is his use of the closed term “Control Unit based Storage Virtualization” – its not the only way to do it Hu. SVC has 3400+ clusters in use every day, with people doing real work on them, not just archive and backup. I’d question the fact that you have an embedded switch in the box, doesn’t this suggest that actually the USP is just a big THICK appliance that happens to have some disks in the same rack, and hides the backend fabric under the covers – oh and has serious IO/s limitations on each internal switch port. Conceptually not radically different from SVC, except SVC doesn’t have the very low port limitations. You could indeed configure SVC with some ports dedicated to a ‘hidden’ fabric with just storage and SVC ports. Package that in a 19″ rack and some funky doors… (thats a lot of money to pay for some nice doors)

Anyone interested in the ‘Global Cache’, just consider how it handles caching across different capabilities of external storage. Oh yeah, they don’t recommend you do it…. SVC 4.2.1 recently introduced cache paritioning that protects applications against mis-behaving backend storage, thus Global Caching really isn’t all that great a headline.

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