Transfer Rate Not Equal Between Two Drives

[BigBox]

Hello all,

I've got a weird, although relatively minor, issue that's driving me nuts.

I've got two identical 3TB My Book Essentials here. Both are at the same firmware rev and are set up exactly the same. Both are currently hooked to the same PC via the same USB3 controller. They are identical in every way that I can tell.

The issue is that one drive consistantly acheives faster transfer rates during writes of large files than the other one. The first drive will run writes of large files at an average of around 75Mb/sec. The second one, though, only delivers around 60Mb/sec on the same files.

As I noted, everything I can think of is identical between these two drives - I've even swapped the cables and the USB3 ports they are on with no effect. Whatever is slowing down the second drive is related to the drive itself.

I know, it's a minor issue. I'll live just fine with either of those transfer rates. I'm just mystified by what might be causing it and concerned that it may be a sign of problems developing with the second disk.

Anybody have any ideas?

Cheers,

Big.

[Awopero]

Mate,

The USB transfer speed is not steady.

[BigBox]

Just to clarify . . .

I'm talking about average speeds with large (>30Gb) files that take several minutes to transfer.

While I agree that instant transfer speed will vary dramatically from moment to moment that doesn't address the phenomenon I'm seeing between these two drives having significantly different average transfer rates on the same files and system.

Thanks,

Big