Understanding The Speed Differences of USB Portable Drives

The disk platter on a USB portable hard drive is driven by a small motor internal to the drive. The time required by any disk operation is controlled by the rotational speed of the drive motor. The most common speed found on USB portable drives is 5400RPM. Other speeds available are:4200RPM; 7200RPM; 10,000RPM; 15,000RPM, although 10,000 and 15,000 are uncommon and drive the cost up significantly.  Disk Speed can affect operations in three ways:

Seek Time

Seek time is the amount of time it takes the disk heads to be positioned over the desired location on the disk. If there is no disk ongoing, the disk controller does not know where the heads are at any given time. The disk manufacture placed a readable index point on the drive at manufacture. When a disk operation is called, the disk controller waits for the heads to read the index point, then it starts counting until the heads reach the desired point. This time interval is called seek time. Once the heads reach the desired point, data can begin to flow whether reading or writing.

Data Flow Rate

The faster the disk is spinning the faster data can flow on or off the disk to the processor.

Disk Fragmentation

Data is deposited onto a disk surface after the heads reach the first available blank space. If there isn't enough space at that point to accommodate the entire file, the controller proceeds to the next blank space and continures the process until all of the data is written. This can result in a file being scattered all over the disk surface. Not to worry, the computer remembers where it put everything but it will take more time to write or read when it is scattered. Fortunately, Microsoft Windows has a tool commonly called the "Disk Defrag Tool". This tool can be found at Start>Help and Support>erformance and Maintenance. This tool will rearrange the data by moving files and data around until the parts of a file are in contiguous sectors, thus reducing the time to find and read/write the data. The program, depending on the size of the disk can take a significant amount of time. I leave my system on and run it at night. Unfortunately, the disk must be run manually and by that I mean you must select it and run, and it should be done about 1 time per month.  You should also note that your USB portable drives need to be defragged as well as your main system drives.

What Speed Do You Need?

Dsisk speed is not of any real significance if you will only be using your USB portable drives for word processing, spreadsheets, or surfing the internet. If you are doing disk intensive tasks such as editing video, playing games, file transfers then speed is of consequence and you should go for more speed. Generally, the 7200RPM speed is enough for most SOHO (Small office/home office) tasks. Engineering operations such as AutoCad would benefit from the 10k and 15k disks.