Maximising external disk speed

[FragrantHead]

Having been blown away by the speed of a Samsung 830 SSD in my T520, I decided to run a simple test. I used a program that writes out a file with all zeroes. The result:

In the Ultrabay of a T520 (SATA3): 360MB/s
In the Ultrabay of a T410s (SATA2): 200MB/s
In a Startech eSata cradle: 115MB/s (regadless of laptop)
Via a USB2 adapter: 22MB/s (regardless of laptop)

This has been a very informal test, but what's a bit perplexing is that, other than the T520/SATA3 result, which is probably the true speed of the drive, none of the other tests are even close to the theoretical speed of the interfaces. SATA2 should allow close to 300MB/s, eSata similar (presumably) and USB2 should allow more like 50MB/s, or have I got that wrong?

That the drive is that fast in the T520 is really exciting for virtual machine backups and other unwieldy files. FYI, I use TrueCrypt on all my drives. There could be a processor induced limit in the SATA2 result, although even the T410s (i5-520M) has the AES-new instructions and shouldn't be bottle-necked by the CPU, I think.

Has anyone else done tests with really fast drives? Tests with conventional disks or older SSDs don't cut it in this context. The Samsung 830 is the only drive, that I've had, that exposes the limits of the interfaces. What I'd like to know is how the USB3 ports in current generation laptops fare vs. the USB3 in, say, an X220 vs. various ExpressCards. Also whether there are external disk cradles or enclosures that are faster than others. My cradles and adapters are probably bottle-necked by whatever (cough, JMicron) chipset they use.

If you have experience with the relative speeds of other solutions, I'd like to hear.

[loyukfai]

It's not unusual for the "real world" speed to be below that of "theoretical" maximum. For instance, there could be control and checksum data involved that will essentially reduce the effective bandwidth to the end-user.

And sometimes it's because of the hardware and firmware implementation.

Cheers.