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Old 03-18-2012, 05:26 PM
David Christensen
 
Default LUKS/ dm-crypt/ ext4 appears to be single threaded

debian-user:

I have a 1.5 TB SATA hard drive I use for back-up's. It has a single
large partition encrypted with LUKS/ dm-crypt and formatted with ext4.
I've noticed what appears to be single-threaded behavior when one
process is performing a long-lived write to the disk (notably 'ssh
user@host tar ... > backupfile.tar.gz') and another process attempts to
access the disk (either read or write). This is tolerable for a back-up
application, but would not be acceptable for multi-user, multi-process,
and/or multi-threaded applications (file server, terminal server, web
server, etc.).



Is this a fundamental limitation of LUKS, dm-crypt, and/or ext4, or
something I've configured/ misconfigured?



If a fundamental limitation, is there something I can substitute to
eliminate the problem?



Some manufacturers make hard drives with built-in encryption. Are these
supported by Debian, Linux, or BSD?


http://www.seagate.com/www/en-us/products/self-encrypting-drives/


Any other comments or suggestions?


TIA,

David


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Old 03-19-2012, 12:50 AM
Henrique de Moraes Holschuh
 
Default LUKS/ dm-crypt/ ext4 appears to be single threaded

On Sun, 18 Mar 2012, David Christensen wrote:
> with ext4. I've noticed what appears to be single-threaded behavior

...

> Is this a fundamental limitation of LUKS, dm-crypt, and/or ext4, or
> something I've configured/ misconfigured?

It is a limitation of dm-crypt.

Just get a box with a supported very-high-speed AES hardware accelerator
(e.g. recent amd64/x86-64 processors with AES-NI), and tune your dm-crypt
usage to cyphers that can be hardware accelerated. Even single-threaded
AES-NI dm-crypt would be much faster than multithreaded non-accelerated
dm-crypt, AFAIK.

> Some manufacturers make hard drives with built-in encryption. Are
> these supported by Debian, Linux, or BSD?

Yes, although it often requires proper support from the EFI/BIOS for it to
be usable in the boot device (and also on the image device when using
suspend-to-disk). YMMV.

> Any other comments or suggestions?

You better do your homework if you're going to trust the vendors of
self-encripting devices.

--
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot
Henrique Holschuh


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Old 03-20-2012, 12:48 AM
David Christensen
 
Default LUKS/ dm-crypt/ ext4 appears to be single threaded

On 03/18/2012 06:50 PM, Henrique de Moraes Holschuh wrote:

Just get a box with a supported very-high-speed AES hardware accelerator
(e.g. recent amd64/x86-64 processors with AES-NI), and tune your dm-crypt
usage to cyphers that can be hardware accelerated.


Yes, my next machine will have AES-NI. :-)


But, the problem is processes with a long-lived writes blocking
everything else, not encryption/ decryption speed.



David


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Old 03-20-2012, 02:02 AM
Henrique de Moraes Holschuh
 
Default LUKS/ dm-crypt/ ext4 appears to be single threaded

On Mon, 19 Mar 2012, David Christensen wrote:
> On 03/18/2012 06:50 PM, Henrique de Moraes Holschuh wrote:
> >Just get a box with a supported very-high-speed AES hardware accelerator
> >(e.g. recent amd64/x86-64 processors with AES-NI), and tune your dm-crypt
> >usage to cyphers that can be hardware accelerated.
>
> Yes, my next machine will have AES-NI. :-)
>
> But, the problem is processes with a long-lived writes blocking
> everything else, not encryption/ decryption speed.

Well, you could try the deadline IO scheduler...

--
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot
Henrique Holschuh


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