More on >2TB drives

["Robert G. (Doc) Savage" <dsavage@peaknet.net>]

Following up on my mention at the March SILUG meeting about next-generation hard drives using 4KB sectors to reduce the ECC overhead and make drives >2TB more practical... This from Britain's Thinq (http://www.thinq.co.uk/news/2010/5/17/exclusive-seagate-confirms-3tb-drive/?full):

Exclusive: Seagate confirms 3TB drive Needs UEFI, 64-bit OS and new partition table
After a few weeks of rumours, Seagate’s senior product manager Barbara Craig has confirmed to Thinq that “we are announcing a 3TB drive later this year,” but the move to 3TB of storage space apparently involves a lot more work than simply upping the areal density.

The ancient foundations of the PC’s three-decade legacy has once again reared its DOS-era head, revealing that many of today’s PCs are simply incapable of coping with hard drives that have a larger capacity than 2.1TB.  

The root of the problem is the original LBA (logical block addressing) standard, which can’t assign addresses to capacities in excess of 2.1TB. Originally set out by Microsoft and IBM as a part of the original DOS standard, the original LBA standard assigns an address to each 512-byte sector – the smallest physical block of data on a hard drive.

Unfortunately, though, the range of addresses is limited to capacities of 2.1TB. It’s a limit that until now has seemed so far off in the future that hardly anyone’s considered it a problem. “I think that’s what everyone thought,” says Craig. “Nobody expected back in 1980 when they set the standard that we’d ever address over 2.1TB.”  

Craig explains that “we need to extend that to Long LBA addressing,” in order to get around this. Long LBA basically increases the number of bytes used to define an LBA address in the command descriptor block, but it also requires a supporting OS.  

According to Seagate, this includes the 64-bit versions of Windows 7 and Vista, as well as modified versions of Linux, but it doesn’t include Windows XP. Not only that, but you may not even be able to see 2.1TB of a 3TB drive when using Windows XP.

Seagate says that its own tests have shown that as little of 990MB of a 3TB drive could be available to you when using XP.

“There’s also a GUID partition table (GPT) that needs to be implemented,” explains Craig, “for the master boot record.” Current master boot record partitions are limited to 2.1TB, so a new GPT partition table would also need to be used to see beyond this.

Of course, this is all fine if you’re using a 3TB drive as a secondary disk, but there are more problems to overcome if you want to use that 3TB drive to boot your OS. Unfortunately, the master boot record is a key part of the standard BIOS setup that motherboards have used for decades.  

GPT was originally proposed as a part of Intel’s Extensible Firmware Interface [EFI]; a user-friendly setup system designed to replace the clunky ASCII-based BIOS. This specification is now looked after by the United EFI Forum (UEFI, http://www.uefi.org/home/), and one of its many new features is a larger LBA addressing scheme, which would enable enough addresses to be handed out to drives with greater capacities than 2.1TB.  

However, this presents a big problem, as many standard motherboards don’t feature a UEFI system. Some manufacturers, such as MSI, have introduced UEFI to a select few boards (http://www.msi.com/html/popup/MB/uefi/applied_model.html), but UEFI is still not the de facto standard. What’s more, any RAID drivers, if appropriate, will also need to support Long LBA if you want to put your 3TB drives in an array.  

Basically, with the original LBA limit set at 2.1TB, it seemed pointless for anyone else to prepare for any capacity beyond this, so we now have a situation where many hard drive controllers, BIOSes, drivers and operating systems are all set with caps of 2.1TB, and this is going to take an industry-wide overhaul to overturn.  

Although this involves a massive amount of work, Craig says that “many of the partners - you know the operating system, the BIOS, the RAID controllers - everyone has attacked it, and I think about 80 percent of the infrastructure’s ready to support it.”  

“On the UEFI standard, we’re going to a Plugfest (http://www.uefi.org/events/) next month,” he continues, “to ensure that everybody is ready, and the IDEMA Group (http://www.idema.org/) is also supporting them.” According to Craig, the preparation for the move to 3TB drives has also meant cooperation with other hard drive manufacturers.  

Assuming that all the issues get ironed out, Seagate says that it’s planning to launch its first enterprise-level drives with more than 2.1GB of storage space at the end of this year.