Re: raid0 slower than devices it is assembled of?

[Mike Fedyk]

On Tue, Dec 16, 2003 at 08:42:52AM -0800, Linus Torvalds wrote:
> My personal guess is that modern RAID0 stripes should be on the order of
> several MEGABYTES in size rather than the few hundred kB that most people
> use (not to mention the people who have 32kB stripes or smaller - they
> just kill their IO access patterns with that, and put the CPU at
> ridiculous strain).

Larger stripes may help in general, but I'd suggest that for raid5 (ie, not
raid0), the stripe size should not be enlarged as much.  On many
filesystems, a bitmap change, or inode table update shouldn't require
reading a large stripe from several drives to complete the pairity
calculations.

Probably finding the largest block of data the drive can return in one
command would be a good size for a raid5 stripe.  That's just speculation
though.
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