The Other Shoe Drops

A while back, the change from hard drives with 512 byte logical sectors to 4096 byte sectors was chronicled here, especially as Western Digital was the first to deliver these drives to market. At that time, the drives were said to have no problems with Windows XP once an alignment utility was used to make sure that the reads and writes ended on proper boundaries. The performance penalty was said to be negligible.

That was back in December, before the first of the drives from Western Digital arrived. Then in a February article, I told about the findings that a 230% penalty in write times was found, but the understanding at that time was that it was because of the misalignment.

Now, the problem seems to be constant, and cannot be ameliorated by the alignment utility for Windows XP, no matter whether the alignment is properly done or not. The changeover works well to keep the move to Windows 7 moving for Microsoft, as the articles begin the FUD and fear mongering (as if there was a difference). There is another article in PC Magazine that tells about problems that are not changed by the alignment utility, and shows that 5 years ago, the story was there – a story that, if Microsoft had been “our friend” it would have changed things so that XP would have made this change one of little concern rather than one of grief over the FUD being spread.

It’s been (somewhat) common knowledge for a while now that hard drives are slowly transitioning from using 512-byte sectors to using 4KB sectors. (ExtremeTech reported on it in 2005, for example.) But, as a recent BBC story points out, Windows XP users may be in for trouble when what is currently an “advanced format” becomes the standard next year.

Each 512-byte sector in a traditional hard drive also includes a marker showing where it begins and error correction code (ECC); a small gap also exists between sectors. This is space that cannot be utilized even in large-capacity drives. The change to 4KB sectors could reduce the amount of wasted space on hard drives by as much as eight times, but still allow twice as much space per block for error correction. This is important, as increase in storage space means more errors, and there’s not enough ECC in 512-byte sectors to deal with it all. Each 4KB sector could contain up to 400 bytes of ECC.

The format change also lets hard drive manufacturers build drives with more capacity that use less power. All hard drives will format with 4KB sectors by early 2011.

But users of Windows XP, or other older operating systems, may run into problems as those OSes were designed with the 512-byte rather than the 4KB architecture. XP and older OSes do not automatically align writes on 4K boundaries, though this is something that can be adjusted by use of software provided by the hard drive manufacturer (such as Western Digital’s Advanced Format Align Utility). Some drive imaging or cloning software for PCs also does not yet support 4KB sectors, so if you clone a 512-byte drive you would need to run the alignment utility.

New drives using the 4KB format will be able to mimic 512-byte sectors, but performance may be affected in certain write situations, introducing a delay of approximately 5ms. (Reading data should not take any longer.) In the BBC story, David Burks, a product marketing manager for Seagate, estimates that in some cases the performance hit could be as much as 10 percent.

Per the BBC story, Windows Vista and Windows 7, and Mac OS X Tiger, Leopard, and Snow Leopard will not be affected by the format switch. The BBC story says that versions of the Linux kernel released after September 2009 are also 4KB aware, but OSNews reports that Linux users may run into problems if they create partitions that start on odd-numbered 512-byte logical sectors.

So now that standard support for Windows XP is over, Microsoft can be expected to do nothing, and for those that are bothered by the extra slowness of the problem, the fix for them will be an OS upgrade. The 2005 ExtremeTech article tells how the problem may cause 2 full spins on a complete cylinder write, similar to back when hard drives used an interleave factor.

As anyone using drives that far back knows, if you went from an XT computer to an AT, at 3 times the processor speed you noticed a huge difference when you changed your drive from an interleave of 3:1 (which the first drive I ever had on my AT computer was) to 1:1 (which I did, with much trepidation back then), the difference was like putting things on a rocket sled.  Now if you can imagine going in the opposite direction – that is what this just may be like. That 2005 ExtremeTech article did not sugar-coat the problem, as the recent articles up to this one have have been doing.

This may be a small problem, but it also could affect some who are very sensitive in a big way. One thing to not be afraid of is data loss – unless there is a distinct problem, that nothing else could help anyway, there will be no data loss. The slowing may or may not be a big deal, but to keep out of the possible trap, purchasing one of the current drives that use the old standard, with a size of 750 GB or 1 TB might be the best solution, if you intend to use XP for a while longer, as there will be no help from Microsoft in the matter.

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Hand: A singular instrument worn at the end of the human arm and commonly thrust into somebody’s pocket.Ambrose Bierce

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