Jeff Garzik <[EMAIL PROTECTED]> wrote: > Greetings from your friendly neighborhood SATA kernel hacker!
Hi Jeff, > Drive companies like Seagate and Western Digital are beginning to poke > me about 1K and 4K sector support. > > Specifically, they are referring to drives that will have a 1K or 4K > _physical_ sector size, yet still present the same old 512-byte sector > size to the ATA driver and OS. > > The main need is 1K and 4K sector _alignment_ support. Does parted > already have this? > > Future ATA drives can be odd-aligned or even-aligned. > > Even-aligned 1K drives writing 1K of data at sector #100 will (in "disk > pseudocode") do: > > * seek to LBA 100 > * write data to LBA 100-101 > > Odd-aligned 1K drives writing 1K of data at sector #100 will do: > > * seek to LBA 99 > * read LBA 99-102 > * update data from internal buffer > * write data to LBA 99-102 > > The latter is called a "read-modify-write cycle," and its a performance > killer. Ouch. I can believe that. > Therefore, it is critical that partition alignment matches internal ATA > disk sector alignment, when these 1K and 4K drives come out. There's a lot of alignment-related infrastructure in parted. See e.g., uses of ped_alignment_init in libparted/labels/*.c or just "git-grep align". Maybe all parted needs is a way to determine what alignment is required on these new disks. When are they expected to hit the market? BTW, I spent some time making parted work with sector sizes > 512 a few months ago. Simulating larger sector sizes invariably provoked stack overruns and other nastiness. It's a pretty big mess. I fixed a few, and have some unfinished patches: other projects took priority. Does anyone care about larger-than-512-byte sector sizes? _______________________________________________ parted-devel mailing list [email protected] http://lists.alioth.debian.org/mailman/listinfo/parted-devel
