4K sectors transition: Why are hard drives moving to 4096 byte sectors, vs. 512 byte sectors?

Bar none, this is the best article I have read on the topic:

http://www.anandtech.com/show/2888

In a nutshell, to answer your questions:

• What's the big deal with 4K sectors?

The primary advantage is more efficient use of the raw storage space. The necessary ECC calculations were starting to provide diminishing returns using 512 byte sectors, but they can be done much more efficiently on larger sector sizes.

• Is it marketing hype, or a real advantage?

The real advantage is that drives larger than 2TB will be more affordable and reliable sooner than without the transition. The same idea holds for smaller drives too, but the returns aren't as dramatic. There are some theoretical advantages to having the sector size map to the common allocation size in a volume (4K for NTFS is about as common as dirt) and memory pages are generally 4K in size as well (makes the pagefile/swap happy).

• Why should somebody building a new PC care, or not, about 4K sectors?

Today - the only thing you should care about it is probably not getting one. There are still a few kinks that are being worked out that if you aren't aware of might cause you grief. Windows XP support is one, the drives lying about their geometry is another.

• Why is this transition taking place now? Why didn't it happen sooner?

It has been in transition for many years already, but consumer drives are just starting to appear on the market.

• Are there things to look out for when buying a 4K sector hard drive? e.g. incompatibility?

You probably won't experience a problem with Windows 7 or Vista, but any of the older Microsoft OS's might cause you grief. There is compatibility built in, but because of sector alignment issues it might cause performance degradation.

• Anything else we should know about 4K sectors?

Read the article, brush up on your math, and then read it again. Really it is a good thing and will enable the storage industry to continue forward more rapidly.

512 byte sectors started whenever we had really small media, like less than 300k floppy disks. It made sense then, it doesn't really make sense now. The thing about 4k sectors is that a lot of drives are already using it, but they have firmware faking 512 sectors. This is especially true for flash media and SSDs. I believe 4k is the de-facto internal SSD standard.

So manufacturers just figured to cut out the middle man and let the OS handle the 4k sectors in a way it knows how to(which ends up being better once we get full support for it)

If you're building a new PC it does matter. Some OSs may not support 4k sectors at all(read: older) and most OSs and filesystems still are optimized for 512 byte sectors. One thing that comes to mind is OpenBSD. It currently does not perform as well with 4k sectors compared to 512 byte sectors. Among the problems is partition alignment. By default, the first partition is not aligned on a 4k boundary.

The transition is probably taking place now because of the large surge of SSDs. SSDs like I said use 4k sectors internally anyway, so it's much better to let the OS handle these raw than leave it up to the firmware to try to guess what the OS wants.

I'm sure some old motherboards may have problems with such harddrives, but anything you bought recently(past 5 years) should definitely be compatible.