Messages in this thread | | | From | (bill davidsen) | Subject | Re: Blockbusting news, this is important (Re: Why are bad disk sectors numbered strangely, and what happens to them?) | Date | 21 Oct 2003 20:12:00 GMT |
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In article <11bf01c39492$bc5307c0$3eee4ca5@DIAMONDLX60>, Norman Diamond <ndiamond@wta.att.ne.jp> wrote: | Friends in the disk drive section at Toshiba said this: | | When a drive tries to read a block, if it detects errors, it retries up to | 255 times. If a retry succeeds then the block gets reallocated. IF 255 | RETRIES FAIL THEN THE BLOCK DOES NOT GET REALLOCATED. | | This was so unbelievable to that I had to confirm this with them in | different words. In case of a temporary error, the drive provides the | recovered data as the result of the read operation and the drive writes the | data to a reallocated sector. In case of a permanent error, the block is | assumed bad, and of course the data are lost. Since the data are assumed | lost, the drive keeps the defective LBA sector number associated with the | same defective physical block and it does not reallocate the defective | block.
Sounds right to me. If you relocate the LBA sector then on retry I will (a) read {something} without error, and (b) it will NOT be my data, and (c) I will not get back an error to tell me I am reading crap. In other words, to do anything else would result in my silently getting back bad data!
What should be done is to relocate after successful retry or after unsuccessful write, because in both cases the drive has valid data to relocate.
Blockbusting news, I think they're doing it just right. The object is not to do a read and get no error, the object is to read and get correct data, and if that doesn't happen, let the controller, o/s, or application know about it decide what to do then. -- bill davidsen <davidsen@tmr.com> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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