

Theodore Ts'o: Aligning filesystems to an SSD’s erase block size - wmf
http://thunk.org/tytso/blog/2009/02/20/aligning-filesystems-to-an-ssds-erase-block-size/

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mtarnovan
Implementing DEALLOCATE/TRIM in the SSD's firmware seems like a good solution.
It's weired that an Intel engineer would say (in an article refered to by this
article [http://www.behardware.com/articles/731-6/ssd-product-
review-...](http://www.behardware.com/articles/731-6/ssd-product-review-intel-
ocz-samsung-silicon-power-supertalent.html)) that _Today, there is no ATA
protocol available to tell the SSDs that the LBAs from deleted files are no
longer valid data._ As far as I can tell, protocol extensions regarding
trim/deallocate were specified by T13 (<http://t13.org>) as proposals as early
as 2005.
([http://t13.org/Documents/UploadedDocuments/docs2007/e07154r1...](http://t13.org/Documents/UploadedDocuments/docs2007/e07154r1-Data_Set_Management_Proposal_for_ATA-
ACS2.pdf)):

 _Deallocate(Trim)

Deallocate shall be set to one to indicate the data set no longer needs to be
maintained. The host expects to write this data set before it reads it again.
If a read occurs to any part of the data set before it is written, the device
may return the data stored from its previous write or it may return all 0s._

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wmf
Implementing proposals is risky because the standard might change. Once
Windows 7 is released SSDs can start implementing whatever commands it uses.

