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[Discuss] TrueCrypt with SSD

> From: Derek Atkins [mailto:warlord at MIT.EDU]
> Dell Laptop (E6420) using Fedora's default-install dm-crypt
> configuration.  The performance hit was in how long it took to copy
> ~300GB of data from a USB (or eSata) drive.  When I did a similar copy
> on an unencrypted ThinkPad it took a fraction of the time that it took
> to copy it on the encrypted Dell.  Same Data.  The only differences were
> the ThinkPad v. Dell, and encrypted v. non-encrypted.  Even the copy
> method was using the same, on the same base OS.
> I just dont recall if I had upgraded to 2.6.40 before or after copying
> all the data....

That's a plenty modern processor.  As I said, and others have said the same
thing, the most cpu overhead you'll see, depending on your processor and the
encryption algorithm, is 1%, 3%, 20%, 30%...  Never 100% and therefore never
a slowdown resulting.  Unless you're doing something horribly wrong like
AES-Blowfish-Serpent-whatever...  Quadruple encrypted 16M bits...  Or
something horrible.

I suspect your slow down is not caused by the encryption.  Or else there's
something horribly wrong with your encryption.  Maybe you have the wrong USB
drivers loaded and therefore the external drive is really slow... 

Some tests that might shed some light on the subject ...

Simply write a file.  Eliminate the possibility of external drive slowdown.
time dd if=/dev/zero of=10Gfile bs=1024k count=10240

Run top during the process.  Watch to see if there's some other process
competing for CPU.  Watch to see if the CPU ever reaches 100%.

Eliminate encryption entirely.  Just read the file and dump to the bin...
time cat /media/usb-external/bigfile > /dev/null

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