Re: RAID stripe size (was: 5.1 RAID5 write performance)

[buhrow%lothlorien.nfbcal.org@localhost (Brian Buhrow)]

        Hello.  I like this explanation.  Can you help clarify by giving a
theoretical example?
-thanks
-Brian
On Jun 6,  9:50am, Thor Lancelot Simon wrote:
} Subject: Re: RAID stripe size (was: 5.1 RAID5 write performance)
} On Mon, Jun 06, 2011 at 03:24:15PM +0200, Edgar Fu? wrote:
} > > Ah, yes, the old 
rmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmwrmw
 cycle.  Gets me every time.
} > OK, I've fixed that (before doing the tests I reported the last two days).
} > 
} > So, what's the advantage of a larger sectPerSU?
} > It appears to me that the raidctl manpage should note that
} > -- the stripe size should match fsbsize
} 
} Wait.  I didn't notice this until just now.  This is not right.
} 
} The filesystem block size (or, where this is not possible, the maximum
} cluster size the filesystem will write) should be equal to sectPerSU
} times the number of data (not parity) disks.  The sectPerSU value is
} the *per-component* stripe size, not the total amount of data written
} across all components in one stripe.
} 
} Thor
>-- End of excerpt from Thor Lancelot Simon