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56 pointsoctosphere14 comments

Weirder than that, there is a second area on the disk which lets you do the same thing

https://en.wikipedia.org/wiki/Device_configuration_overlay

So there are two hiding places instead of just one.

If you're curious, I think this is the original proposal from ~ 1996. It's amazing to see all the old hardware vendors on these things. Gateway and Maxtor are dead now (Maxtor is on the ATA-3 specification). I like that this covers two pretty common use cases. I wonder if the current "sleep" technology of computers does this with the RAM, or if they use another more modern mechanism.

http://t13.org/Documents/UploadedDocuments/technical/d96137r...

> HPA can be used by various booting and diagnostic utilities, normally in conjunction with the BIOS. An example of this implementation is the Phoenix FirstBIOS, which uses Boot Engineering Extension Record (BEER) and Protected Area Run Time Interface Extension Services (PARTIES).

I thought it was interesting that BEER redirects to this page.

https://en.wikipedia.org/wiki/BEER

I didn't realize that Wikipedia was case specific:

https://en.wikipedia.org/wiki/Beer

Vs.

https://en.wikipedia.org/wiki/BEER

It's not 100% case-insensitive: the first character cannot be lowercase, so https://en.wikipedia.org/wiki/a and https://en.wikipedia.org/wiki/A are the same article.

If you're wondering if NSA or others are using it for their purposes, yes, they are:

https://www.schneier.com/blog/archives/2014/02/swap_nsa_expl...

Warning: contains TS classification markers. If you have clearance you might not want to click that.

HPA was also a good way to overprovision SSDs for better write performance before TRIM existed (although today's SSDs are so fast I would no longer worry about overprovisioning).

Samsung Magician still recommends overprovisioning, even for the newer NVME SSDs.

I think Magician just leaves 10% free at the end by changing the partition size, it does not seem to set a HPA or use DCO. If you started with a secure erase/factory clean SSD, those blocks will be marked as unused and the garbage collection algorithm can play Sokoban with them however it wants.

It’s depends on the ssd. HPA works well for some DCO is often a better choice for most vendors.

Also I think of this as a wear protection rather than a performance, increase.

Even before SSDs it was also used to short-stroke spinning HDDs for better random seek performance.

I mean if you wanted to go full tinfoil hat, that thing hits the spot.

If you're trying to hide something then that's a TERRIBLE place to put it.

I'd highly recommend something like veracrypt where you can encrypt a container, and the container may or may not have another part encrypted with a different password - you don't know until you enter the correct password for the hidden section.

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