On Sat, 2009-07-18 at 13:04 -0700, Dan Williams wrote:
On Sat, Jul 18, 2009 at 11:42 AM, David Woodhousedw...@infradead.org wrote:
On Sat, 18 Jul 2009, Dan Williams wrote:
I was under the impression that btrfs wanted to leverage md's stripe
handling logic as well, seems that is not the case?
No. We do a bunch of the stuff you mention above, but entirely within the
file system so we don't have to invent a bunch of layering violations just
to work around a broken design.
Sure, a layering violation for an existing filesystem. For btrfs, at
LSF'09, we briefly talked about breaking out more than just the
erasure codes from software-raid into a libraid. At some point in
the i/o path a btrfs stripe operation becomes indistinguishable from a
raid5,6 operation so at first glance there appears to be room to share
common infrastructure like portions of handle_stripe for example.
At this point we've actually implemented the fundamental parts of
RAID[56] support in btrfs, and it's looking like all we really want is
the arithmetic routines.
Perhaps that's because I'm insufficiently familiar with the
handle_stripe() function to which you refer. Would you like to take to
take a look at http://git.infradead.org/users/dwmw2/btrfs-raid56.git and
attempt to convince me that I should be reusing more?
Criticism in 'diff -up' form is always welcome... :)
--
David WoodhouseOpen Source Technology Centre
david.woodho...@intel.com Intel Corporation
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