Re: Miserable Disks

Optimal for single session?  Maybe.  Isn't this roughly what RAID-2 was
supposed to do?
Of course, even then, it's really only optimal if the platters all spin and
the heads all move
synchronously, isn't it?

I was under the impression that this is why RAID-2 is rarely implemented.
(Normally,
I'd say "never implemented", but on this list, I just *know* somebody would
correct me...)

I don't know, really.  Probably for single-session applications, especially
those doing huge
sequential I/O, you'd do quite nicely with just two or three of those
"Stinking Huge (TM)"
ATA disks that make us shudder whenever our PHBs mention them.

;-)

Sadly, I've never bothered to benchmark this configuration, but I *am*
pretty confident that
it will be far less-than-optimal for most concurrency levels much greater
than 1...



On 5/26/06, Jared Still <jkstill@xxxxxxxxx> wrote: 

Comments inline.


On 5/25/06, Mark Brinsmead <pythianbrinsmead@xxxxxxxxx> wrote:

>
> (*) Make your RAID stripe width really narrow (like maybe 128 or 512
> bytes) and then
> make your database blocks large (like 8KB or 16KB) and do lots of
> multi-block I/O,
> so that every I/O is assured to engage every physical drive.  (Kiss
> concurrency goodbye
> and watch your RIOPs numbers plummet)
>

Seems like somthing like this might be optimal for single session.
Benchmarks? ;)






--
Cheers,
-- Mark Brinsmead
  Staff DBA,
  The Pythian Group
  http://www.pythian.com/blogs

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