Does it make any difference what kind of hard drive I buy to put in an external USB 2.0 enclosure in terms of transfer speed?

October 17, 2011 7:57 PM

Does it make any difference what kind of hard drive I buy to put in an external USB 2.0 enclosure in terms of transfer speed?

So I have an empty external USB enclosure. Given that USB 2 has a low data rate relative to SATA does it make any difference if I buy a low-power slower drive (e.g. 5400 RPM) vs a higher-performance drive (e.g. 7200 RPM)? I'm fine spending more to get a faster drive but I'm unsure how much of a bottleneck USB 2 is in practice and whether all drives will perform mostly the same once in an USB enclosure.

posted by GuyZero to Computers & Internet (4 answers total)

It'll matter some in seek time (not a lot, but is measurable) but not in serial reads or writes. USB2 tops out here on my drives at 30 - 40 MB/sec. That's so close to the theoretical limit of USB2 that I'm 99% sure the USB link is the bottleneck. Even my crappy original 5400 rpm laptop drive could hit ~ 70 MB/sec, so I think you're fairly safe picking a low-power drive.
posted by introp at 8:03 PM on October 17, 2011

The case you linked to says it has an eSATA port - if you use that, there's no bottleneck so a faster drive in the enclosure will make a difference.

If you just use the USB 2.0 port, you'll be capped at ~40 MB/s as introp says, and they'll be no appreciable difference between modern drives.
posted by unmake at 8:16 PM on October 17, 2011

Why did I forget that my PC has an eSATA port? That was the whole reason I bought this enclosure. Man, my memory.
posted by GuyZero at 8:57 PM on October 17, 2011

Assuming you are doing the thing that is equal to optimal for maximum throughput conditions, any drive will work in USB mode. Assuming you care about heavy random access, faster drives are faster even when connected by USB. drives with bigger caches also offer real benefits depending on your work loads.
posted by fief at 9:15 PM on October 17, 2011