On 11. juli. 2009, at 16.59, David Woodhouse wrote:
On Fri, 2009-07-10 at 10:58 +0200, Roy Sigurd Karlsbakk wrote:
I know it's not in yet, but is there a plan to implement raid-z(2)-
like operation? I have heard of plans to integrate with the existing
md-subsystem in the kernel, but I'm not sure if this will be
appropriate comparing this to how things are done in zfs/raid-z.
I'm currently working on the basic implementation of RAID5/RAID6 (qv).
I don't think there'll be much integration with the md subsystem --
we'll probably just shift the cunning GF arithmetic out into lib/raid6
or something, then let them both use it from there.
We do want to do full stripe writes to the RAID[56] parts, so we're
going to want to do something like falling back to RAID1 (or to a
RAID5
chunk with smaller stripe length) for smaller allocations. That's
basically what you're talking about, isn't it?
In ZFS/RAIDZ(2) they are said to use RAID3-like partial writes as with
with a file-level redundancy, meaning if a file won't cover a whole
stripe, it'll use a partial one. I'm not sure if this is the case, but
it's what I've been told by the people from Sun. This may open for
fewer IOPs per write. Is something like this in the thoughts of the
new RAID[56] in BTRFS?
roy
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Roy Sigurd Karlsbakk
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roy@xxxxxxxxxxxxx
http://blogg.karlsbakk.net/
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