This message is from the T13 list server.
On Fri, 27 Jun 2003 13:44:26 -0700, Nathan Obr wrote: >I do assume that drive manufacturers will do the right thing, but that >is only because they have for years. Are you sure? What is the definition of "right thing"? Is it some test Microsoft uses for logo certification? Is it just some feeling that everyone is doing the "right thing" so there is no problem? I don't understand why you seem to have no concerns about this. >The only requirement that a host >has on a device with a cache is that the cache doesn't change the >behavior of the device. What behavior? Where is that defined? Is there some standard for how a disk drive is supposed to work? Is there a standard for how a disk drive cache should work? If such standards exist I've never seen T13 or ATA/ATAPI-x reference them. Does Microsoft have a document that describes in detail how a disk drive works and/or how a disk drive cache works? If so, can you share it with us? >Any caching scheme that returns data for a >sector other than the last data written to that sector has a design >mistake, Huh? It would not be a "design mistake" if the manufacturer product specification defined that their drive did not operate in that manner. And I can think of design reasons to implement a drive in a manner that you would call a mistake. Sure that may not be a "good design" but there is no standard that would say it was invalid/illegal. If you or Microsoft think such implementations are not possible and/or would never happen then I think you and Microsoft need to learn more about how disk drives are operate and how they are designed. >however, I don't believe any caching algorithm is considered >"valid" to ATA/ATAPI as I am not aware that ATA comprehends caching. Hmmm... ATA/ATAPI-x define SET FEATURES commands to turn read/write caching on/off and then there are the FLUSH CACHE commands. Maybe ATA/ATAPI doesn't define how read/write cache should operate but ATA/ATAPI does allow the host some control of this drive activity. >I believe that device caching behavior is outside of the scope of the >ATA protocol and off topic for this forum. Perhaps, but again that just reinforces the need for an answer to my questions above, especially the question of where is the specification or standard or Microsoft document that defines how a disk drive and/or a disk drive read/write cache are implemented. In another email to the list today you said FUA should not cause hardware changes in a drive (I think that is what you said). Before you assume FUA is so simple I think you need to talk to some disk drive designers. Hale *** Hale Landis *** www.ata-atapi.com ***
