Alan Cox wrote:
First generation of 1K sector drives will continue to use the same
512-byte ATA sector size you are familiar with. A single 512-byte write
will cause the drive to perform a read-modify-write cycle. This
configuration is physical 1K sector, logical 512b sector.
The problem case is "read-modify-screwup"
At that point we've trashed the block we were writing (a well studied
recovery case), and we've blasted some previously sane, totally
unrelated sector of data out of existance. Thats why we need to know
ideally if they are doing the write to a different physical block when
they do this, so that we don't lose the old data. My guess is they won't
as it'll be hard.
I think that the firmware would have to do this in the drive's write
cache and would always write the modified data back to the same physical
sector (unless a media error forces a sector remap).
If firmware modifies the 7 512 byte sectors that it read to do the 1 512
byte sector write, then we certainly would see what you describe happen.
In general, it would seem to be a bad idea to do allocate a different
physical sector to underpin this king of read-modify-write since that
would kill contiguous layout of files, etc.
A future configuration will change the logical ATA interface away from
512-byte sectors to 1K or 4K. Here, it is impossible to read a quantity
smaller than 1K or 4K, whatever the sector size is.
That one I'm not worried about - other than "guess how Redmond decide to
make partition tables work" that one is mostly easy (be fun to see how
many controllers simply can't cope with the command formats)
This will be interesting to find out. I will be sharing a panel with
some BIOS & MS people, so I will update all on what I hear,
ric
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