[dm-crypt] aes-xts-plain with aes_x86_64 makes my SSD 5x slower than my encrypted HD

Marc MERLIN marc at merlins.org
Thu Aug 16 09:43:33 CEST 2012


On Sun, Aug 12, 2012 at 03:49:29PM +0300, Pasi Kärkkäinen wrote:
> I didn't read the whole thread, but are you aware that many/most SSDs use
> internal processors for compression, deduplication, etc .. 
 
Yes

> so if you write encrypted data to the SSD, it's not able to do it's internal magic,
> and thus you get a lot worse performance compared to non-encrypted data.

Only on some controllers like sandforce, the Samsung 830 wasn't supposed to
be affected

> So did you try benchmarking with *random* data *without* encryption? 
> Also always first write to the disk, and only read after it has been already written to.

Yes, both were parts of my tests.

But, I owed everyone an update, which I just finished typing:
http://marc.merlins.org/perso/linux/post_2012-08-15_The-tale-of-SSDs_-Crucial-C300-early-Death_-Samsung-830-extreme-random-IO-slowness_-and-settling-with-OCZ-Vertex-4.html

Basically, the samsung 830 just sucks. I got 2 of them, they both utterly
sucked. There is no excuse for an SSD being several times slower than a slow
hard drive on _READs_ (not even talking about writes).

I'm not sure how I could have gotten 2 bad drives from Samsung in 2
different shipments, so I'm afraid the entire line may be bad. At least, it
was for me after extensive benchmarking, and even using their own windows
benchmarking tool.

In the end, I got a OCZ Vertex 4 and it's superfast as per the benchmarks I
posted in the link above.

Cheers,
Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/  


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