Saturday, June 20, 2009

HPA

Host Protection Area was introduced in ATA-4 to allow computer vendor to save data that would not be erased when a user formats the hard disk. It is intended manufacturer to stow diagnosis tool and backup image so that they do not need to ship an install CD.

HPA was an area set aside at the end of the disk using SET_MAX_ADDRESS command. The command featured a "volatile" bit which allow the HPA to be effected at the next reboot. This allows user to read/write the HPA in the current session and lock the content after reboot.

HPA is invisible to both BIOS and OS.  It is managed by low level ATA commands.


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