On 03/24/10 22:54, Stefan /*St0fF*/ Hübner wrote: > Am 23.03.2010 23:10, schrieb Nebojsa Trpkovic: >> Hello. >> >> I've found interesting text about TLER / CCTL >> (http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery ) > > You might want to read on inside the ATA8-ACS, section about SCT Transport. >> >> on desktop class drives: >> http://forums.storagereview.com/index.php/topic/28333-tler-cctl/ >> >> So, the question is: >> >> If I make my drive report back it failed to read the requested sector, >> how that report will be handeled? > > As far as I understood in recent answers to my questions: as expected. >> >> Will Linux software RAID be aware of that report and start some action >> (rebuilding affected stripe or at least whole array, reallocating bad >> sectors along the way) ? >> > Indeed. Michael Tokarev answered to me on 2/9/10: > "On failed _read_ it tries to > reconstruct data from other disk drives and writes the reconstructed > data back to the drive where read failed. If the _write_ fails md will > drop the disk." > > This means: if read fails and the drive does not report back, the > following reconstructing write calls will fail, too. The disk gets > dropped, because it (most probably) is still doing its error recovery on > the former read request and by that not responding. > > If you enable ERC read timeouts, it'll report a media error (or > something similar), but honour the write request. If you give the ERC > write timeout a value that is not too small and also not too large (i.e. > it shouldn't timeout the write-operation from the view of the kernel), > it will either fix the pending sector, or reallocate it. If the ERC > write timeout value is too small, it'll very aggressively reallocate > sectors - which should not be the intention, as there are very few spare > sectors (compared to the amount of sectors in total - only a few thousand). >> >> Thank you. >> Nebojsa Trpkovic > > You're welcome, and all the best, > Stefan > Thank you very much! This is great answer (explaining a lot of things) and great news (there's nothing to worry/hack about). So, now we (desktop drives users) just have to wait for smartmontools 5.40 or pull source from SVN and set some reasonable ERC read timeouts. Is value of 7 seconds considered as reasonable ERC read timeout? Nebojsa -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
