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Joerg Schilling wrote:
From [EMAIL PROTECTED] Fri Jun 4 21:14:23 2004
3.2 Read Capacity (10) Command (25h)
() BLOCK LENGTH IN BYTES
This value is currently set to 512 bytes,
which is the standard sector size for disk drives.
I see us taking the chance to try to fix the bytes/LBA at 0.5 Ki, like MMC fixed the bytes/LBA at 2 Ki, shutting out the (empty set of?) ATA MO folk.
I like that.
It shut out nobody.
IMO the OS request block size _should_ be constant at 512 octets. It makes calculations easier, and representations more normal.
Please do not forget CD/DVD writers.
They use 2048 Bytes per block.
That's fine, it's a multiple of 512.
It's rather nice when the kernel block or filesystem driver can simply store a shift count, and then do
BASE_SECTOR_SHIFT=9 dvd_wr_sector_shift=2 device_sector_shift=BASE_SECTOR_SHIFT + dvd_wr_sector_shift block_bytes = (1 << device_sector_shift)
Storing things as a power-of-2 is very efficient on a number of host platforms. And basing things off of a fixed base -- 9 (512 bytes) -- makes life even easier.
Jeff
