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HDD Manufacturers Moving To 4096-Byte Sectors

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Senior Forum Spammer
Jun 6, 2002
at first it looks like nothing...
For quite some time now, mechanical hard drives have stored data in 512-byte chunks called sectors. That sector size worked for lower capacity points, but as areal densities rise, it's become increasingly inappropriate for new drives. As a result, the industry has decided to transition to a 4KB sector size dubbed Advanced Format.

So-called legacy formatting schemes sandwich each 512-byte sector between Sync/DAM and ECC blocks that handle data address marking and error correction, respectively—and also take up space. You still need those blocks with Advanced Format, but only every 4KB rather than every 512 bytes, which translates to a dramatic reduction in overhead. This approach allows Advanced Format to make more efficient use of a platter's available capacity, and Western Digital expects it to boost useful storage by 7-11%, depending on the implementation. Current 500GB/platter products stand to see an increase in useful capacity of about 10%, which is really quite impressive.
has more to do with it being more effective to use 4096 with higher density drives...


Jul 7, 2006
what does this do for performance ?

hard to tell as there are many factors when comparing retail drives. In theory it should increase performance but not enough to market 4K drives as faster then 512 drives. BTW they are in the wild now in certain countries but not sure if they are in the US now.

It looks like the 1TB EARS (the new green with 64mb cache and the new blocks) performs worse then the two platter 1TB EADS (00M2B0 and 00P8B0 both with 32mb cache) baised on preliminary data. It will obviously outperform the older 3 platter EADS models though.

They are close in speed but the older 500gb platters appear to have better seek and min transfer rates. The new model appears to have a higher max transfer and slightly higher average transfer but the drop in speed is sharper resulting in bad mins. Again this is prelim data so it may be faster but the drop off is shocking in this design.

This switch has been mentioned here and there for years now as coming but western digital is the first to do it. Personally I think they took the risk because their 500gb platters haven't been up to par and there have been allegations of yield issues that these new platters may have fixed.

BTW although they say it will result in size gain it won't for consumers, at least for the current line of 500gb platters. This merely allows WD to make slightly smaller platters which should increase yields. Both the new EARS and the old EADS format to the same size.
Last edited:


Dec 16, 2007
Chicago, IL
Upgrading Legacy standards is always good :)

The anandtech article had a good explanation about it. It has to do with how much space ECC takes up using different sector sizes. (Way less ECC space required with the new sectors for the high density platters).

I don't think it does much for speed, just space. HDD's are pretty slow to begin with.