[dm-crypt] Advanced format (4k sector disks) and dm-crypt

Garðar Arnarsson gardar at giraffi.net
Sun Jan 19 19:07:39 CET 2014


Thank you very much for the reply and explaination.
I suspected that there was not a concern to dm-crypt in regards to 4K
sectors since I did not find any mantion of it when searching the web
and it's good to have that confirmed.

On Sat, Jan 18, 2014 at 7:36 PM, Arno Wagner <arno at wagner.name> wrote:
> On Sat, Jan 18, 2014 at 20:24:47 CET, Arno Wagner wrote:
>> On Sat, Jan 18, 2014 at 15:14:29 CET, Garðar Arnarsson wrote:
>> > Did a quick search but came up empty handed.
>> >
>> > I'm wondering if there is anything special that needs to be passed to
>> > be able to use dm-crypt (cryptsetup) with 4096 byte sector drives.
>> >
>> > I know md, lvm, partitions, filesystems all need to have special
>> > triggers for 4K drives (even thouh I think it's done automatically for
>> > all of them nowadays) but I see no mention of dm-crypt/cryptsetup.
>>
>> Do not worry. Dm-crypt uses 512B sectors, but there is only a
>> negligible performance loss. This matters far, far more on the
>> filesystem layer. If that layer does it right, dm-crypt will
>> allways process 8 x 512B at a time, as it does process exacly
>> what the uppeer layer requests. And alignment in LUKS is done
>> so that 4k sectors will not be broken up for the data area.
>>
>> Hence this is not a concern and that is the reason it is
>> not mentioned. I think I will add an FAQ entry for this.
>>
>> Arno
>
> Just added Item 2.17 to the FAQ.
>
> Arno
> --
> Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
> GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
> ----
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