is 10 MB second normal for a USB 2 drive?

[swingerofbirch]

I backed up my iMac HD today to a new external hard disk. It's a Western Digital My Book Personal Edition 160 GB USB 2.

I know it's not the fanciest model but to back up 123 GB of data it took 3.5 hours. Is that normal? I used SuperDuper and it said it was averaging 10-11 MB per second transfer.

I called Western Digital and the guy said if I wanted speed I should have gone with FireWire. He said USB 2 has bursts of 60 MB per second, but that 10 MB per second was pretty average. I thought it was 480 as a burst level?

I kind of remember that USB 1 had a limit of 12 MB/sec....is it possible for some reason it was only running at USB 1 speeds? I'm using an iMac C2D which has USB 2 of course, and the cable I used I presume is USB 2 compatible as it came with the HD.

 

[plinden]

USB max is 480 Mb/s (that's Megabits) is 60 MB/s, so that is right. USB 1.1 had a 12Mb/s max transfer rate.

As for sustained transfer rates, I get about 38MB/s reading and 30MB/s writing with Firewire 400 on my external drive.

The same drive with USB 2 is 14MB/s reading and writing.

That's copying a large 1.5GB file. Transfering lots of small files (as you do when backing up a HDD) would lower the average.

 

[Schroedinger]

I agree with Plinden. Also, there are other factors to take into account, such as whether the drive in question is busy doing anything else, whether your system is doing anything else, yada yada. You're as likely to get full transfer speeds as you are likely to get the quoted battery life of an ipod.

However, I don't think you made a bad choice. I use firewire for external media that contains, well, any sort of media files. I'll use external USB 2 for back ups b/c you aren't going to be doing giant full back ups too often (I hope). With an incremental back up system, especially an automated one, those slow speeds won't be an issue and the cost per gig is better and hopefully you'll never need to get info back off of it (and if you do, you'll just be happy to have it.)