On Wed Jan 06, 2010 at 02:58:16PM -0500, Curt Hartung wrote:
> Tried to ferret out the answer to this myself and so far so bad.
>
> This just 'popped in there' while I was optimizing something completely
> different... in a RAID-1, writes have to be mirrored of course, thats
> what RAID-1 is, but for reads, could they not be sped up by a
> significant amount if a storage pattern was chosen such that large
> blocks of data were "striped" in an in-order/out-of-order scheme? In
> other words, store all the data on both drives, but in huge (2x cache
> size) -ish blocks that might allow 50% of a given [large] access to come
> from each drive, with trivial [smaller] reads always coming from one or
> the other chosen at random.
>
> Downside, I know, is that the data would be organized ina way only the
> raid subsystem would understand, so the niceness of pulling a mirrored
> drive out of service and it being a literal copy of the otehr drive
> would be lost, but for such a speedup I'd be willing to pay the price of
> always having to access it as a failed set (worst case) through the
> md-daemon.
>
> Am I off into the weeds?
I doubt this would help much really. If you're reading sequential data
then it's pretty much as quick to keep reading as to seek to the next
chunk. If you want a performance and are prepared to throw out strict
RAID1 compatibility then RAID10-f2 may be better suited. It still
provides the same redundancy but improves read performance by striping
(there's some slowdown on writes but not much).
Cheers,
Robin
--
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( ' } | Robin Hill <robin@xxxxxxxxxxxxxxx> |
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