March 17, 2003

137GB HARD DRIVE LIMITATIONS

The smallest hard drive we sell anymore is a 40GB.  We sell these by the truck-load because most people don’t need anything larger.  However, with the growing popularity in video, audio, and large data file storage, we are seeing hard drive capacity grow beyond certain limitations.  One such limitation is the 137GB mark for most controllers.  Currently we are using ATA-5 controllers.  In detailed terms ATA-5 is limited to 137GB because there are a maximum of 28 bits for addressing the logical block of cylinders, heads, and sectors. When you do the math, this equates to a maximum of 137GB that can be recognized by the controller.  The drives we are seeing these days that exceed that capacity are ATA-6.  This technology raises the addressing bits from 28 to 48.  Once again let me do the math for you.  Our next limitation will be 144 petabytes.  Q:What’s a petabyte?  A:A thousand terabytes.  Q:Whats a terabyte? A:A thousand gigabytes.  Is this starting to sink in? Our next limitation is a long long way off.  It is so far off that data storage technology will probably change to another format before we get there.  The one thing you may be overlooking is the operating system limitations.  Current Windows platforms including XP are 32 bit.  (Yes I know, 64 bit is already out there.)  Anyway, the current O/S can’t recognize a drive larger than 2.2 terabytes on a single disk.  Although 2.2 terabytes seems huge, remember Moores Law.  “Computers will double in speed and capacity every 18 months….forever.”  This law has stayed true and is on track for a long time.  (See newsletter archive from April 13, 2001New Lease On Life for Silicon)

There is a problem with our current situation that everyone should be aware of.  If you purchase a drive larger than 137GB ATA-6 and install it on a ATA-5 controller, when the drive capacity hits 137GB, you will run into the wrap-around affect.  Instead of telling you that the drive is full something very bad happens.  First of all, an ATA-5 controller will recognize a drive with capacity over 137GB.  Therefore you may think you have the ability to use the entire drive.  However, the controller does not know how to handle this situation and it starts overwriting your data at the beginning of the drive!  The next thing you know you have lost all your data.  137GB of data isn’t easy to recreate. (Note that some of the Maxtor hard drives are not true ATA-6 and will not experience this problem.)

The solution to this problem is simple.  An ATA-6 controller.  We will write more on this fix as information becomes available.  We are researching several different fixes as we speak.  We will provide information on Serial ATA, Firewire etc. so you can understand all the options available.  

S&K