Ok, so let recap:
1) FAR layout is the one depicted by SuSe documentation, while the
Wikipedia entry is wrong
Yes.
2) MD _can_ produce a FAR layout as depicted by Wikipedia, but we don't
know how the user-space mdadm tool call it (maybe it is not implemented
yet?)
Yes. Not implemented yet.
3) There are any reasons why FAR and OFFSET layout scramble data in this
manner, coupling any disk with two more disks? It was done for
simplicity, or I am missing something?
It just seemed the easiest thing to do at the time.
4) you confirm that currently we can _not_ create a FAR layout as the
one depicted by wikipedia by no means? What about OFFSET layout?
You certainly can created the FAR layout depicted on wikipedia, e.g. by
binary-editing the metadata on some devices, or writing some code which does
that for you. It requires flipping one bit in the metadata and updating the
checksum. You can probably even to it by writing something appropriate into
some sysfs files.
But mdadm cannot do it yet.
Ditto for the new OFFSET layout.
(The old offset layout can be created with "--layout=o2").
NeilBrown
All clear now :)
Thank you very much Neil.
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