Re: hdparm-9.2 now available: w/ DCO and firmware support

[Mark Lord <liml@rtr.ca>]

Greg Freemyer wrote:
> On Tue, Nov 4, 2008 at 1:08 PM, Mark Lord <liml@rtr.ca> wrote:
..
>> Mmm.. never thought about that much before now,
>> but DCO is a nifty way to hide much of a drive from prying eyes.
>> Eg. Use DCO to restrict the drive to LBA28 accessible sectors
>> and also turn off LBA48 support, and then a lot of space becomes "hidden".
>> Until now!
> 
> Yeah, combine that with some HPA shenanigans and you can create two
> complete disk partition layouts on one drive.
> 
> ie. Two partition tables, the normal partition table for the first 128
> GiB is in sector 1.  The partition table for the rest of the disk is
> at sector 128 GiB + 1.  Then use DCO to totally hide the upper section
> of the drive.
> 
> When you want access, use DCO commands to expose it, and then HPA
> commands to make only the sectors beyond 128 GiB accessible.
..

Now that one has me stumped.  The only HPA commands I know of,
permit setting only the maximum-LBA, not the minimum.
Or is this a newish ATA9 (or last-minute ATA8) sort of thing ?
..
> to the end of the disk, then issue a "hpa swap" command.  That will
> hide the first 128 GiB and expose the rest of the disk.
..

Yeah.. what's this "hpa swap" ?  Possibly a vendor-specific op, perhaps?

Cheers