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Date: Wed, 14 Jul 2010 14:53:02 +0200
From: Milan Broz <mbroz@redhat.com>
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Subject: Re: [dm-crypt] Wrong behavior?
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To: Sven Eschenberg <sven@whgl.uni-frankfurt.de>
Cc: dm-crypt@saout.de

On 07/14/2010 02:07 PM, Sven Eschenberg wrote:
> I don't see why cryptsetup does not end up with 1024 sectors (which is
> the optimal_io_size) - or is the luks header bigger than 512k? even
> bigger than 1 MB (2048 sectors) ?

yes. not header, but space for 8 keyslots.

Alignment is multiple of caclulated size - keyslot takes a lot of space.
Add --debug - you see required alignment there, then code must take
into account keyslots size.

So you have 2048s optimal IO size, I expect you are using 512bit key,
so alignment using default 4k is 4040 sectors (only space for keyslots).

So code must align to next multiple of 2048 - it is 4096.

Milan