Keld Jørn Simonsen wrote:
On Wed, Jul 16, 2008 at 01:58:05PM +1000, Ben Martin wrote:
On Tue, 2008-07-15 at 18:39 +0200, Keld Jørn Simonsen wrote:
On Wed, Jul 16, 2008 at 12:06:09AM +1000, Ben Martin wrote:
One interesting question about the r10 layouts, if f2/o2 perform better
than n2 why is the default for creation still n2? Just like mkfs.xfs
determining the raid chunk and stripe size for you (assuming you don't
use LVM to circumvent this, gah!), shouldn't mdadm select the "fastest"
--layout as the default for RAID-10?
Perhaps. I think Neil first implemented "near", and more or less at the same
time "far" - but to him the main thing was "near". This was 2.6.9. Then
in 2.6.18 he implemented "offset". In the early days the
characteristics of each layout were not well known. It is only in the
last year or so I have seen benchmarks with n2, f2 and o2.
I admit that I have done "raw device performance" benchmarks with n2 and
f2, and neglected o2 completely, so I rely on other's work. However, I
am most often bitten by raid5 issues, so I have been paying most
attention to them.
--
Bill Davidsen <davidsen@xxxxxxx>
"Woe unto the statesman who makes war without a reason that will still
be valid when the war is over..." Otto von Bismark
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