Thursday, 17 June 2010

Data recovery and different USB protocols

When recovering data from a USB external hard drive, you should keep an eye on a data read speed. If the speed is less than 2 MB (megabyte) per second, it would be better to abort the recovery and figure out in what mode the devices are working. The speed is of less concern with smaller devices, that is if you need to recover pen drive, you just sit, watch, and wait it out.

There are two different versions of the USB protocol, USB 1.1 and USB 2.0. From the user point of view, these protocols differ from each other only by a data transfer speed. USB 1.1 transfers maximum ~ 1.5 MB/sec, while USB 2.0 can achieve ~ 50 MB/sec. If several USB devices involved in a data transfer use different USB protocols, the lowest data transfer speed is used.

Although USB 2.0 was developed in 2000, USB 1.1-only hard drive enclosures and card readers are still produced. If you are going to buy a USB enclosure for external hard drive recovery, check that it supports the USB 2.0 protocol. Data recovery from the drive connected via USB 1.1 is too slow to be practically used, because it would take a couple of days or sometimes even weeks to perform a data recovery.

If you use a USB hub you should check it as well. Generally, whenever possible, try not to use any intermediate elements. Some hubs can switch in USB 1.1 mode when many devices are connected via the hub.

On some motherboards USB ports of different versions are mixed. If possible, check the motherboard manual to find out what ports are USB 2.0 and connect to them. If you do not have the manual, simply try a few different ports. Most often there is a difference between USB ports in the front of the case and those located on the rear.

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