Re: [gentoo-user] LUKS

[Richard Fish <bigfish@asmallpond.org>]

On 1/10/06, Boyd Stephen Smith Jr. <bss03@volumehost.com> wrote:
> On Tuesday 10 January 2006 07:13, Cláudio Henrique
> <rapaduraatomica@gmail.com> wrote about 'Re: [gentoo-user] LUKS':
> > What about the performance, is it too different from plain partition
> > usage?
>
> I never noticed the difference when I was using aes-loop on a 2GHz laptop.
> That said, it will depend on the algorithm you choose and the CPU you have
> available.  Also, I /think/ aes-loop was supposed to be faster than
> dm-crypt, but I believe the kernel's implementation of aes (and maybe
> other ciphers) has gotten faster since the last benchmarks I saw.

I tested this recently on my new AMD64 X2 system.  The dm-crypt and
loop-aes are very very close in performance.  I can't really say which
is faster, because for some configurations, dm-crypt was faster, while
for others, loop-AES was faster.  By configurations I mean using 2
disks, software raid, LVM, and dm-crypt/loop-aes, and playing with the
order of the "layers" (do I make a raid of 2 encrypted disks, or
encrypt a raid array of 2 disks, or ...), the block sizes, etc.  And
in some cases, loop-aes would be faster at writing, but dm-crypt would
be faster at reading, or vice-versa.

The one thing I think loop-aes does better is that it creates a
separate thread for each encrypted device, so it can take advantage of
SMP systems.  Still, I ended up using dm-crypt+luks on that system.

For performance, on the AMD64 box, the two disks could deliver a
combined read throughput of around 130MB/sec.  The highest throughput
I got with dm-crypt or loop-aes was 115-118MB/sec read, 95MB/sec
write.

On my 2.13Ghz laptop, using loop-AES, the disk can only deliver a
maximum of 50MB/sec, and loop-aes tops out at about 45MB/sec at 42%
CPU utilization.  The only time it becomes a real impact is when I am
doing a backup, when I have decrypt the data from one disk, archive
it, compress it, and then encrypt the archive when it is written to
another disk.

I do _not_ notice an impact when compiling, becase the amount of disk
activity for a typical compile is insignificant compared to the CPU
usage of the compiler.

-Richard

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