[dm-crypt] (More) Questions about LUKS / LVM

Karl O. Pinc kop at meme.com
Tue Sep 20 20:06:47 CEST 2011

On 09/20/2011 12:41:29 PM, Arno Wagner wrote:
> On Tue, Sep 20, 2011 at 05:21:54PM +0200, Alexander Koch wrote:
> > Am 20.09.2011 13:47, schrieb Arno Wagner:
> > > With an SSD, things are a bit different. Due to the large
> > > internal sector size, the header can be in a sector that
> > > also has data that gets rewritten in it. As sectors are
> > > always written completely, the header then is at risk whenever
> > > that data gets rewritten.

> No connection with TRIM support. It is just that if the real
> block size is larger than the block size you are using,
> the SSD will rewrite/reloacte other data on writes smaller
> that the real sector size. 
> What would need ot be done is to
> 1. Align LUKS header (partition start) to a real sector
>    boundary. 
> 2. Align the start of the filesystem area in that
>    partition to a real sector boundary.
> Both are only possible to do realiably when you know the
> sector size. All of my 3 SSDs claim 512 byte sectors,
> which is almost certainly a lie.

Performance is also going to suck if you don't get
alignment right on drives with 4Kb sectors.

FWIW here are the links I use to deal with 4Kb sector issues.


Karl <kop at meme.com>
Free Software:  "You don't pay back, you pay forward."
                 -- Robert A. Heinlein

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