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> "Daniel J Colegrove" <[EMAIL PROTECTED]> 02/14/02 05:18PM > rev. 1 of e01138 Large Physical Sector Support up on the web site. Fun, thank you. Delightfully concise: just about two pages of substance. Four pages appear now in just 17,641 bytes at <http://www.t13.org/docs2002/e01138r1.pdf>. > allows devices to report > [a fixed ratio of 1, 2, 4, 8, ...] > up to 32768 logical sectors per physical sector Can you explain what motivates limiting the reportable physical/logical ratio to powers of two? > existing systems ... restrict practical > device implementations to 4096 bytes per physical sector. Yes. I hear we face a 4KiB limit wherever we view disk i/o as a random track, serial block, access of 4KiB pages of virtual memory. > 2 Definitions > > physical sector: A group of contiguous logical sectors, > which must be read from or written to the device media > in a single operation. > > logical sector: A uniquely addressable set of 256 words > (512 bytes). > > unaligned write: An unaligned write is a write command > that does not start at the first logical sector > of a physical sector or does not end > at the last logical sector of a physical sector. Delightfully concise enough to be worth quoting. :-) > Unaligned Write ... will incur .... penalty > ... at least a drive revolution. Yes, though I don't yet have a clear picture how much/little help a logical sector cache could reasonably offer. I wonder what kinds of bounded-time guarantees hard drives supply for the flush of their write caches? I've heard of low-end designs that guaranteed errors are never deferred more than one command, but I imagine high-end behaviour is less determinate? Pat LaVarre Subscribe/Unsubscribe instructions can be found at www.t13.org.
