>>>>> "Eric" == Eric Sandeen <sandeen@xxxxxxxxxx> 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
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