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I've noticed that some Western Digital hard drives are now sporting 4K sectors, that is, the sectors are larger: 4096 bytes vs. the long-standing standard of 512 bytes. So:

  • What's the big deal with 4K sectors? Is it marketing hype, or a real advantage?
  • Why should somebody building a new PC care, or not, about 4K sectors?
  • Why is this transition taking place now? Why didn't it happen sooner?
  • Are there things to look out for when buying a 4K sector hard drive? e.g. incompatibility?
  • Anything else we should know about 4K sectors?
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3 Answers 3

up vote 7 down vote accepted

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.

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Also, I believe it equals more storage for the sticker capacity. arstechnica.com/microsoft/news/2010/03/… –  Nathaniel Apr 21 '10 at 23:55

here's an in depth on what and why http://lwn.net/Articles/322777/

Windows XP doesn't support it. Linux userspace tools are not all there yet.

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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.

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What if I write my own OS? Do I still need to care about 4k at the beginning or will it work fine? –  Cole Johnson Sep 8 '12 at 4:23
    
@ColeJohnson it depends. If you're writing your own ATA driver, then yes, you'll have to make sure that your sector size isn't assumed to be 512 bytes. If you're using the BIOS(ala int 13h), then it depends on your BIOS. I imagine some may try to emulate 512 byte sectors for compatibility, but I don't know really –  Earlz Sep 8 '12 at 4:59
    
I thought it was the hard drive hardware that emulated it not bios –  Cole Johnson Sep 11 '12 at 23:16
    
@ColeJohnson it is harddrive hardware. Some BIOSs may have problems booting from 4K sector disks though, or only load 512 bytes. I'm not saying that's the case with any motherboard, but it's a possibility since it was a common assumption years ago that sectors are 512 bytes –  Earlz Sep 12 '12 at 4:49

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