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Date: Thu, 17 Mar 2011 16:08:36 +0100
From: Milan Broz <mbroz@redhat.com>
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Subject: Re: [dm-crypt] HDD sector size interrelated with dm-crypt?
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To: dm-crypt@saout.de

On 03/17/2011 03:29 PM, Lars T=E4uber wrote:
> does dm-crypt depend in any way on the sector size of the block
> device to be encrypted? So the real question is: Does dm-crypt work
> as expected on a 4KiB sector sized SATA drive when there is no
> translation to 512B sector size? Are there options that must be taken
> then?
>=20
> I've read somewhere that the encryption algorithm work with 512B
> block sizes. Could this be changed to 4KiB block sizes to gain speed
> with the upcoming devices?

dmcrypt always uses 512 bytes sector for encryption, it cannot be changed
easily to 4k sectors (internal block layer bio structure and device-mapper
always counts in 512 sectors).
I do not think that with accelerated encryption like AES-NI the speed up
would be so visible.

But the whole stack (including device-mapper) properly aligns
to drive sector size, so it will work with 4k drives without problems.
I think many people is already using it on true 4k drives.
In fact mapping sector is the block layer problem, device-mapper targets
just propagates block size information up the stack.

Milan