USB Harddrive performance oddity 1

[jsteph]

Hi all,
I'm trying to figure out why I'm seeing such a huge performance difference copying files to a WD MyBook external drive.

There are two computers in this scenario--mine and my son's. The Mybook drive is connected directly to my computer via USB (I have only USB 2.0 on my machine but the MyBook is a USB 3.0 but is compatible).

My son's machine is connected via a hardwired gigabit line to my router, which is also hardwired to my machine.

I mapped a folder on the MyBook to my son's machine, so for example, he connects to the MyBook as:
\\DadsMachine\MyBookShare

So he's going through the ethernet, to the router, through ethernet again to my machine, then through my machine's USB 2.0 to the MyBook, and he's getting 65 MBps steady throughput over 4 Gigs of random files in a test folder, with bursts over 80 MBps.

Yet, when I copy the exact same test files from any of my harddrives to the MyBook, I'm only getting 20 MBps!? I'm going straight to the USB interface--no ethernet no router, and I'm less than a third the speed.

My HD's are WD caviar black units and test out with HDTach at 230 MBps burst, and about 110 MBps average read speed. His test out around the same--so there's no real difference on the reading end of things. And of course thy're both writing to the same Mybook drive. The difference is the path taken to that drive and it seems my son's makes a lot more hops over more bottlenecks, just to get to the same USB interface.

So why is his so fast and mine so slow? My machine isn't doing anything else in the backround, task manager is pretty idle.

Both machines are Windows 7 Pro, his a Core 2 Duo 2.1 Ghz 4Gig ram, mine an i7 3.1 Ghz with 6 Gig.
Thanks for any help on this odd issue.
--Jim

 

[kjv1611]

Jim,

I didn't read the latter part of the story, b/c I think the evidence is in the early part.

Here's what I think is happening:

When your son is transferring the files, those files are first being cached somewhere on your machine, and thus what he's getting are the transfers direct from your machine.

That's the only possible way this could happen.

It's either that, or you're reading something wrong. It's not all that common to get those kind of speeds over ethernet and a wired router... well, not that I've seen anyway. Supposedly with Gigabit everything, you can, but it can be tricky with making sure all the hardware pieces in the puzzle are truly up to par with that.

Also, on your USB transfers, 20MB/sec sounds possible, not out of the ordinary. The most you could hope for out of USB 2.0 would be maybe 35 MB/sec in reality. If you had a RAID array of SSDs on each end of a USB 2.0 connection, you'd still only max out around 35 MB/sec.

That's why I say IF the LAN speed measurement is truly correct, then it's due to caching - there's NO WAY to get that speed off a USB 2.0 hard drive, period.

Or if there is, I've got a LOT to learn, and so have all the folks who have posted numerous reviews, blogs, etc, online.

 

[jsteph]

kjv,
I think you're right. I looked in the disk properties and on my machine I did not have write-caching, but on his the network could do the caching whether I have it set that way or not--so what you're saying makes sense.

I then enabled the write-caching (or the 'performance' option where you've got to use the 'safely remove hardware' thing), and my speed then came up to similar to his--but of course it isn't really written to the drive that fast...if I yanked the cord when the transfer ended I'm sure I'd be missing data or it'd be corrupted.

Anyway, my USB 3.0 card should arrive today so I'll see how that goes.
-Jim

 

[jsteph]

Just an addendum...
I added the USB 3.0 card and it tripled the raw speed of the WD harddrive. With HDTach and the original USB 2.0, it was an even 35 MBps for both sequential read and Burst--which is more or less showing that it's operating at the max USB 2.0 speed--so the Burst can't be higher because it's hitting the max.

With the 3.0 card, it was fairly even 110 MBps sequential read throughout the whole range, and the burst was 135 MBps.

So the USB 3.0 is a definite advantage...though I wouldn't call it "Speed beyond your imagination" as the marketing said...but it was without a doubt a substantial boost.
--Jim

 

[kjv1611]

Jim,

I'd suggest it's still fitting to say "speed beyond imagination" when comparing to USB2.0. What you're now seeing is the limit of the actual hard drive, not the connection. And frankly, it's not the limit of the one drive, but whatever the weakest link int he chain is - either that drive, or whatever other drive or array you're sending/receiving data with. Frankly, that's a VERY good speed to be seen for real-life transfers.

If you had SSDs and/or RAID arrays on both ends of that USB 3.0 connection, you'd probably see much higher rates, but otherwise, I wouldn't hope for much if any more than what you're currently seeing.