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I have this SATA-to-USB3 external 2.5" HDD enclosure, connected to a USB2 port, because my laptop doesn't have any USB3 ports.

But it has:

  • a free eSATAp port (power over sata on an eSata+usb2 combo port), and
  • a free expresscard slot.

I could buy:

A) either an eSATAp enclosure like this (to replace my usb3 enclosure) and connect it to my laptop's eSATAp port, or

B) an "expresscard-to-USB3" card like this and connect my usb3 enclosure on it.

I believe that both scenarios would work much faster than the current 480Mbit/s setup (usb3 enclosure to usb2 port), but which one would work faster? A or B?

My laptop doesn't support Sata III. Only Sata II. So the eSATAp port has a maximum speed of 3Gbit/s, right?

On the other hand, my laptop's expresscard drive uses the PCI express 1X interface, which is capable of 2.5Gbit/s. So, the 5Gbit/s USB3 port on the express-to-usb3 card would be bottlenecked to 2.5Gbit/s maximum, right?

Thanks in advance and please excuse my poor English.

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  • In either example ExpressCard and USB2 is going to be the bottleneck
    – Ramhound
    Commented Nov 29, 2017 at 1:52
  • For the record, I re-read your question several times to see if I'd missed any instances of "pool English" and found none. ;)
    – chew socks
    Commented Nov 29, 2017 at 1:59
  • :) I'm always a bit insecure because English is not my native language.
    – gpanousos
    Commented Nov 29, 2017 at 5:59

2 Answers 2

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Accounting for both the USB overhead (which is actually pretty significant), and the PCI-e overhead, the eSATAp connection will almost certainly be faster. It's not normally an issue for things that only do small transfers (like mice and keyboards), but with the constant bulk streaming usually seen with block storage devices (like hard drives), it starts to become pretty significant. I would expect the SATA connection to be measurably faster in terms of throughout and latency.

Additionally, USB is kind of notorious for poor reliability for long term usage. A bus reset (as happens when you bump the connector and interrupt the connection for a split second) is extremely expensive with USB compared to SATA, and is much more likely to cause data corruption.

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Yes, you have the ideas about right. From a speed POV, the eSATAp enclosure would be the better option because it has greater bandwidth, but also because its talking the SATA protocol, it does not require overheads and latencies of converting between protocols. Its also less likely to have driver issues.

I do note that while, in practice, you would expect a slight increase in speed from SATA 2

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