On Thu, 10 Sep 2009 11:32:43 -0400 Luis Useche <use...@gmail.com> wrote:
> Claudio: I don't think FS2 assumptions are completely out-dated. If > this were true, many of the file systems and I/O schedulers > optimizations based on locality would not work (I guess this is a > discussion for another thread). Luis, I'm an NDA-slave, so there's tons of stuff I can't touch or talk about, but the sad truth is, you'd need to work in the storage industry (and sign countless NDA's) to understand all the reasons why Claudio is absolutely right. Modern storage devices have an abstraction layer built into hardware so the device appears to the OS as being something different that what it really is, and hence, the operating system (and coders) have no idea how the device really works. Even if you had all the strategic partnerships and NDA's in place with a specific storage vendor in order to learn their company secrets of how their devices really work, you'd be forbidden from divulging the methods by writing open source software optimized for the device. It truly sucks. Worse yet, it is a trend in hardware, so open source operating system developers keep being further removed from how the hardware they own really works. For lack of a nice way to say it, the vast majority of storage devices you can buy these days are really nothing more than "hardware blobs" that you have to run on faith. This is not to say outdated optimizations of yesteryear have no effect, but the real problem is, without the closely guarded secrets of how things really work, you will never know why there is an effect or what the effect really is. In other words, you're stuck with nothing more than the results of your own empirical testing... -I flip this lever up, and the light goes on. -I flip this lever down, and the light goes off. -But if I want to know how it actually works, then I need to be a multi-million dollar company with a strategic alliances and NDA's in place with all the manufacturers of the equipment I own. It sucks. And it's getting worse. -- J.C. Roberts
