Can you keep a secret? This encrypted drive can...

[Jason Holt]

On Sat, 4 Nov 2006, Ralf Senderek wrote:

> On the unencrypted filesystem:
>
> # > time dd if=/dev/zero of=cryptogram bs=1MB count=50
> 50+0 records in
> 50+0 records out
> 50000000 bytes (50 MB) copied, 0.216106 seconds, 231 MB/s
>
> real    0m0.257s
> user    0m0.000s
> sys     0m0.252s

Unless you have a disk array in your laptop, that performance is an artifact 
of buffering.  Here are unbuffered and buffered numbers for my rather new 
desktop machine:

$ hdparm -t /dev/sda

/dev/sda:
  Timing buffered disk reads:  174 MB in  3.01 seconds =  57.79 MB/sec


$ hdparm -T /dev/sda

/dev/sda:
  Timing cached reads:   5188 MB in  2.00 seconds = 2595.82 MB/sec

The 25MB/sec number for your encrypted partition looks like it's probably 
right, though:

$ openssl speed aes-256-cbc
[...]
The 'numbers' are in 1000s of bytes per second processed.
type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes
aes-256 cbc      52071.66k    55008.98k    55609.83k    55984.13k    55776.36k


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