Unused space on hard drives recovered
Regarding article "Unused space on hard drives recovered?" at this URL.
I am the "Linux SATA guy".
First, users are usually amused to learn that the capacity of modern hard drives is _unknown_, until it goes through the factory's qualification tests. The 120GB hard drive you purchased may have been physically identical to a 250GB hard drive, but simply it only passed qualification at 120GB.
Intel does the same thing with processors. A 3.0Ghz processor may be sold as 2.4Ghz, simply because it didn't pass qualification at 3.0Ghz but did at a lower clock speed.
Second, in the ATA standard there is a feature known as the "host protected area". This area is accessible from any OS -- but it requires special ATA commands in order to make this area available to the OS.
Third, all hard drives reserve a certain amount of free space to use for reallocation of bad sectors. These "spare sectors" are free space on your drive... completely unused until your hard drive starts finding problems on the physical media.
So this is old news
Although the host-protected area (HPA) can be used for insidious purposes such as DRM/CPRM that is completely hidden from the users, most of the "invisible free space" exists for a purpose --
either it's spare sectors for bad sector remapping, or its capacity that didn't pass factory qualification, that you don't want to use anyway.
Feel free to edit/reproduce/publish this email.
Jeff Garzik