Tech Tip: External Hard Disk Drives

If you’re thinking of buying an external hard disk drive for your computer, here are a few things to remember:

• Of the different ways available to connect, USB is by far the slowest.  And it slows your computer down when it is being used.
  
  Every bit of data that goes to and from USB devices has to be handled by your computer’s CPU.  This not only makes data transfer to and from your external USB hard disk drive slow, but it also slows down the rest of your computer as well.  Other interfaces, like FireWire and eSATA, are able to transfer data directly to your computer’s memory without going through or waiting for the CPU, making them much faster.  eSATA will be the fastest, but not very many computers have eSATA ports on them yet (especially laptops).  FireWire is more common, but still not available on lower end computers.  Desktop computers can have an add-in FireWire or eSATA card installed relatively inexpensively.  Speed-wise, eSATA is faster than FireWire is faster than USB.
   
• Generally speaking, bigger hard disk drives are faster than slower drives.
  
  The size of the actual platters containing your data remains the same, so bigger disks have to pack more data into a given area than smaller ones.  The more densely the data is packed, the more is read by the drive each time the platter spins a single rotation.
   
• Generally speaking, bigger drives are more prone to failure.
  
  Because the data is packed more densely, the net loss of any portion of the disk going bad is much more noticeable.  The higher density is more sensitive to imperfections in the disk platter surface.  Bigger disks also tend to use newer, and thus less time-tested, technologies.
   
  I never buy the newest disk drives.  I always wait until a drive has matured before I will consider investing.
   
• For USB and FireWire external hard disk drives, rotation speed doesn’t affect actual performance a whole lot.
  
  Manufacturers usually advertise the rotation speed of their drives, usually 5400 or 7200 RPM.  Just because a drive is 5400 RPM doesn’t necessarily mean it is going to be a lot slower than a 7200 RPM drive.  Especially if you are comparing a larger 5400 RPM drive to a smaller 7200 RPM drive (see the second principle, above.)
   
  For FireWire and USB drives, the performance bottleneck is the drive’s connection to your computer, not the speed of rotation.
   
• As far as power consumption and heat issues go, 5400 RPM drives are a better choice than 7200 RPM.
  
  Drives that spin slower use less power and generate less heat.  And tend to last longer.
   
• Brand name makes some difference, but outside of purchasing an external drive marketed by one of the major manufacturers, you never know what you’re getting.
  
  The major drive manufacturers (Seagate, Western Digital, Samsung, Hitachi, Fujitsu, Toshiba) market drives under their own names.  Other companies sell external hard disk drives, but usually use drive mechanisms from one of the big manufacturers, and there isn’t any way to know what brand of drive you’re actually getting.
   
  I have been buying Seagate drives for years without any issues, and that is what I generally will recommend. Hitachi drives have also been good for me.  My track record with Western Digital has been iffy.
   
• External drives which plug directly into your network, allowing multiple computers to access their contents at once, do exist, and they can be convenient in some ways, but they can be difficult to setup, and they are going to be the slowest of any external drive solutions.  They are called NAS devices (Network Attached Storage), and they can be a little pricey.
   
• The happy medium between price and storage size right now is 1 TB for 3.5” drive mechanisms, and 500 GB for 2.5” mechanisms.  Going much bigger than that generally demands a hefty price premium.
   
• If a drive fails, you will lose everything on it.  So it might be better to have two smaller external drives than one huge drive.
   
• Some manufacturers are offering great warranties (some Seagate drives have a 5 year warranty!), others are just 90 days.  Read the packaging closely.  Every hard disk drive is going to fail someday, and even the best won’t make it much beyond 3-5 years.  Having a good warranty will get you a replacement when yours dies.
   
• Having a good warranty will allow you to get a complimentary replacement, but it won’t get your data back when a drive fails.  Always store multiple copies of your data in different places.

Generally speaking, for best performance get eSATA or FireWire before getting USB.  USB is available on nearly all computers, where FireWire and eSATA are not.  Check to see what ports your computer has.  Get a drive that is going to have sufficient storage for you for a few years, but don’t go excessively large.