On Wed, Feb 9, 2011 at 2:36 PM, Phillip Susi <psusi@xxxxxxxxxx> wrote: > On 2/9/2011 10:37 AM, Alan Cox wrote: >> Unlocking the HPA is actually necessary for sanity on a lot of systems > > Right.. ones that were partitioned using an older kernel with the buggy > behavior of unlocking it by default. > >> too, and there are really no standards. Remember the primary use of HPA >> has actually been to hide most of the disk from buggy BIOSen so that the >> OS can then unlock it after the BIOS has stopped looking. > > The ATA spec describes the HPA saying: > > A reserved area for data storage outside the normal operating system > file system is required for several > specialized applications. > > This tells me that it is intended for the bios to reserve an area of the > disk that the OS should NOT access. So far the only use of it that I > have seen is by bioses to hide a small area, presumably to store > platform specific information. I see about a dozen reports on the > ubuntu forums and bug tracker each year of people with HPA problems and > it always seems to be a small area, as opposed to hiding everything > above 128 MB or something. > Philip, At some point (maybe 10 years ago), Dell used a HPA hidden partition to hold a diagnostic partition of some sort. I never used it, but I remember coming across it several times. I don't recall how big it was. I assume their thought was to have a recovery / diagnostic area that normal users couldn't get to. Now they just use a normal partition for that. I gather fakeraids now use a HPA protected to hold metadata for how the raid is built, but I may have that wrong. Greg -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
