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>2TB Hard Disks

K

KennyG

n00b
Joined
Jul 1, 2005
Messages
11
How far off are we?

It's been more than a year since WD set the current size limit in Jan 2009. The hard disk industry seems to have hit a wall with the HBA 2TB limit (?). Will there be new disks increasing capacities any time soon? Will we get to 3.2TB drives or go straight to 4TB or 5TB disks? Rumors, thoughts, hearsay?
 
Not that soon i think. The problem is that 2TB is a hard limit in many ways:
  • To access anything beyond 2TB, you need 64-bit LBA; 48-bit LBA goes up to 2TB
  • To actually use more than 2TB, you need GPT style partitions; the old fdisk partitions go up to 2TB also
  • To make this bootable, your OS needs to support GPT boot, not sure if BIOS support is required for GPT as well.

So you will both need a new partition scheme (GPT) and 64-bit LBA access.

Perhaps there's a way to circumvent these limitations. For example by using 4KiB sectors or what WD calls "Advanced Format". The problem is that these WD EARS drives do not advertise 4KiB sectors; they still tell the operating system they have 512 byte sectors. That would mean fdisk style partitions are limited to 2TB.

With 4KiB sectors aka "Advanced Format", it would be able to address up to 16TB using the old fdisk/48-bit LBA method. But that would only work if the harddrive actively advertises 4KiB sectors; meaning the OS cannot read or write less than 4096 bytes; any I/O has to be a multiple of 4096 bytes; so it can only read 4KiB/8KiB/12/16/20/24/28/32/~/1024 etc. but nothing in between those values. This may upset older operating systems like XP.
 
Somewhat recent thread covered this question:

http://hardforum.com/showthread.php?t=1498740

in short, 5 x 500gb platters would = 2.5tb, so 2.5tb is possible at the very least. Add in the switch to 4K sectors and 3tb doesn't sound too far off. The only question is when....and nobody can really guess on that except the hard drive makers who aren't telling :p
 
5 platters? Nah only Hitachi went that far, to be the first with an 5x400GB 2TB drive.

But you might see 640GB/platter disks soon; meaning you get a 3-platter 2TB disks; right now these disks are still 4-platters.

Next would be 750GB/platter; giving you 2-platter 1.5TB disks and 3TB 4-platter disks. The 3TB disk would have to use 4KiB sectors; or it will only be usuable by 64-bit LBA systems.
 
Yea, I know it's unlikely....but possible! Just not plausible ;)
 
sub.mesa said:
  • To access anything beyond 2TB, you need 64-bit LBA; 48-bit LBA goes up to 2TB
Click to expand...
Eh? 2^48 * 512b = 128PiB

So the one issue that requires special hardware isn't an issue. The rest are software problems, but legitimate ones. Any 'nix box from the past few years should have no trouble. I think Windows 7 should work with larger drives as well, but I'm not sure if the bootloader supports booting from them. I haven't tried, but I think it's also possible to use multiple fdisk partitions on a > 2TB disk to access the whole disk (up to 4TB), since they're stored as a start sector, length pair.

I haven't heard of any engineering brick walls that are being hit, so I don't expect 2TB to be a long-term limit, but it wouldn't surprise me at all if the hard drive manufacturers waited a bit until penetration of systems that will support such drives well increases. Doesn't it suck having to wait for Microsoft to catch up with the rest of the world? :|
 
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