On Jan 9, 2011, at 6:37 PM, NeilBrown wrote:
Also:
3: <#raid_devs> <meta_dev1> <dev1> .. <meta_devN> <devN>
This doesn't allow offsets into the various devices like dm-stripe,
dm-linear, dm-raid1 all do.
This is a conscious choice. The offset was discarded because it is
unneeded.
Famous last words!!!
:)
When reshaping a RAID5/6 to change the chunk size or layout, or when
converting an N drive RAID5 to N+1 drive RAID6, it makes it a lot
easier if
you can can change the data offset at the same time. Then you don't
have to
keep backing up data. md cannot do this yet but I hope to add the
code soon
and because 'data_offset' is a distinct value it is conceptually
easy to do.
If 'data_offset' is assumed to be zero, then it isn't.
I guess I don't understand this part. Why would you need to change
the data offset? Especially the offset as it relates to the
individual drives?
But I don't know to what extent you are planning on supporting
reshaping of
arrays....
I don't see a reason why this can't be completely supported...
brassow
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