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Date: Fri, 23 Apr 2010 00:20:49 +0200
From: Richard Zidlicky <rz@linux-m68k.org>
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Subject: Re: [dm-crypt] LUKS - SSD trim
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To: Felix Blanke <felixblanke@gmail.com>
Cc: dm-crypt@saout.de

On Thu, Apr 22, 2010 at 10:12:37PM +0200, Felix Blanke wrote:

> scooter ~ # hdparm -tT /dev/sdb3
> 
> /dev/sdb3:
>  Timing cached reads:   18686 MB in  2.00 seconds = 9354.32 MB/sec
>  Timing buffered disk reads:  758 MB in  3.00 seconds = 252.61 MB/sec
> 
> scooter ~ # hdparm -tT /dev/mapper/ssd 
> 
> /dev/mapper/ssd:
>  Timing cached reads:   17432 MB in  2.00 seconds = 8725.18 MB/sec
>  Timing buffered disk reads:  158 MB in  3.02 seconds =  52.36 MB/sec
> 
> 
> The first value is perfect, then second one really sucks.
> Obv. /dev/mapper/ssd is the decrypted /dev/sdb3
> 
> Any idea about that?

dm-crypt is slow - and when it is read I don't think alignment will do any difference. 
loop-AES might be faster.

Richard