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Date: Fri, 18 Sep 2009 15:40:48 -0400 From: "Martin K. Petersen" <martin.petersen@...cle.com> To: Eric Sandeen <sandeen@...hat.com> Cc: "Martin K. Petersen" <martin.petersen@...cle.com>, ext4 development <linux-ext4@...r.kernel.org> Subject: Re: [PATCH, RFC] mke2fs: get device topology values from blkid >>>>> "Eric" == Eric Sandeen <sandeen@...hat.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 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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