On Wed, 2013-07-24 at 06:57 +1000, NeilBrown wrote: > New feature in 3.3 is that when you reshape (e.g.) a RAID5 to a RAID6 it can > do so without using a "backup file" - which is are a pain to work with and > slow things down a lot. > What it does instead is move the "data_offset" towards the start of the > device. That way it is never writing onto live data, and so no backup is > needed. So you are stealing my precious space, which I was paying soo much money for?! ;-) Seriously,... sounds like a good idea... :) But why does it also increase the "gap" at the end? Guess the whole "gap" at the end thingy is something we will never ever really get rid of, will we? I mean it's no problem because of some missing sectors... it just makes like more complicated when doing manual geometry calculations... While talking about data_offset... is it planned to implement a way to add a way to specify the data_offset manually and/or specify a data_offset_offset (i.e. a additional offset to what mdadm would have autodetected... similar as LVM allows? I mean the practical relevance is probably not that much... but manual specification would probably needed whenever you have some more complex block layer (e.g. LVM), another MD or a hardware RAID below MD... and you want to align to the stripes... or unusual large chunk sizes... I've seen that you have some branch where you can specify the offset for each device... but... guess that was only for some guys to do recovery works?! Thanks, Chris.
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