Sorry if this is off topic, and doesn't really solve the problem of having to downgrade to use larger drives. But I have discovered a way to use as much as 1.86TB. No such disk exists, and as you're aware, the PS3 can't simply partition the disk to use only the max supported space on a 2TB. However, it IS possible to modify a disk's firmware to make it appear to the PS3 as a smaller disk than it really is. To do this you have to take advantage of a feature set in the ATA specification to create a "host protected area" on the disk that is hidden from the PS3 (and most operating systems). A 2TB disk has 3907029168 sectors. Reducing this by 7% to 3633537126 sectors will allow a PS3 running 4.46 firmware to format and successfully boot using such a disk. That seems to be the absolute limit. Any higher than that, the PS3 will format a larger size than that, but it will black screen on boot (believe me, I tried through trial and error, and had to blank the first few sectors on the disk after each attempt to make the PS3 boot again each time I'd formatted with a larger size than the PS3's kernel would accept as valid, in between each time I'd changed the max sector count!) Upgrading the PS3's firmware as far as the latest (at time of writing) Rebug lite 4.82 from that point on, and it remains fully functional.
Why would you want to do this, wasting 7% of a 2TB disk? Well, consider the fact that 1.75TB disks are getting very scarce, 1.5TB disks will likely go the same way. 2TB disks are cheaper in my experience and will likely be the easiest to get hold of going forward. This is one way you can get the maximum possible space for your PS3. Note: this was tested on CECHA and CECHC models. I cannot speak for later models, so you may get different results and have to try different max sizes on newer models. To set the max sector size, you will need a program capable of sending raw ATA commands to the hard drive. I personally used HDAT2 on a DOS bootable USB stick. One more note: you may have to plug the disk into the computer *after* it has booted into DOS from your USB stick. Most modern motherboards' BIOS automatically issue a "freeze lock" command at POST to lock these disk settings down, possibly to prevent viruses tampering with your hard drive. Either way, it forces you to have physical access to the inside of your computer while you're doing this. Also, you MUST connect using a SATA cable, you CANNOT do this with the drive connected via USB. If anyone would like a tutorial on how to use this information, please let me know.