You wrote your answer while I was composing mine 
You put ESATA in brackets before I read it.

Thank you for your replies.

Well, I didn't tell the whole story 
I'm going to use it as High Definition Storage where files might be around 1-8GB for 1 file. That's where speed matters unpacking RAR files and stream the stuff over the LAN.

Are you talking about a USB or eSATA hard drive?


Too bad there's no real speed benefit for the eSATA. I guess I'll wait for the GuruPlug Benchmarks and reconsider my plans - although I think the speed result will be the same (since the hardware is almost the same).
And I have to give up my software encryption plans 

If I would buy the e-SATA version of the Sheevaplug and connect it to a 1GBit router and e-SATA hard drive I will get a theoretically transfer rate of 125MB/s from the Sheevaplug to my Desktop computer since the bottle neck is the 1GBit router. I was fine with the idea but then I read this benchmark: http://computingplugs.com/index.php/SheevaPlug_Performance#Network_Performance
If my interpretation is correct - the bottleneck is not the 1GBit router but the CPU of the Sheevaplug which will not allow a transfer rate above ~25MB/s.
So an USB 2.0 version and an USB 2.0 HDD would do the job (and save me some money). Can anybody confirm that the Sheevaplug is limited to less then 30MB/s over LAN?

Besides I'm interested in encrypting my data. I found the Western Digital My Book Essential with hardware encryption. Since it is hardware encryption it should not effect the CPU of the Sheevaplug to decrypt the data. The problem is you need the Western Digital Tool to "mount" the hard drive and after I wrote an e-mail to the support they confirmed there is no linux version of the software. Is there alternative software which can "mount" the hard drive without the Western Digital Tool?
If not - what is the performance of software encryption and which software do you use? TrueCrypt, Loop-AES?

Thanks in advance.