Re: [PATCH, RFC] mke2fs: get device topology values from blkid

["Martin K. Petersen" <martin.petersen@oracle.com>]

>>>>> "Eric" == Eric Sandeen <sandeen@redhat.com> writes:

>> Also, are you guys affected by the
>> previously-acked-sectors-are-now-gone problems with 512-byte
>> logical/4KB physical drives?

Eric> previously-acked-sectors-are-now-gone?  I guess I haven't been
Eric> keeping up.  What do you mean by this?

We already discussed this on irc.  But in case anybody else are
wondering...

On a disk with 4KB physical blocks emulating 512-byte logical blocks the
drive firmware must resort to read-modify-write cycles and that opens up
a new error scenario:

4KB physical block: |                       0                       |
512b logical block: |  0  |  1  |  2  |  3  |  4  |  5  |  6  |  7  |
                                                                 ^ ERROR

In this case we have successfully written LBA 0 - 6.  However, when the
drive attempts to write LBA 7 it gets an I/O error and the previous 7
logical blocks (that have previously been acknowledged as written) are
lost.  IOW, the drive write atomicity is at the physical block level and
not the logical ditto.

See http://oss.oracle.com/~mkp/docs/ls09-topology.pdf page 19 for
prettier graphics.

-- 
Martin K. Petersen	Oracle Linux Engineering