Am 11.03.2010 13:25, schrieb Iain Rauch: >> On Thu, Mar 11, 2010 at 3:51 AM, Iain Rauch >> <groups@xxxxxxxxxxxxxxxxxxxxxx> wrote: >>> Smartd emailed me to say I have "1 Currently unreadable (pending) sectors". >>> This actually happened for two disks now. >>> >>> I ran a check and then a repair on my array and they both gave mismatch_cnt >>> of 8. >>> >>> I ran a long self-test on both and they completed without error with no >>> errors logged. Yet the 'Current_Pending_Sector' is still 1 on both, and one >>> disk also has a 'UDMA_CRC_Error_Count' of 1. >>> >>> I ran 'hdrecover' on both and they are both telling me "Couldn't recover >>> sector 2930277168". It's asking if I want to overwrite it with zeros to fix >>> it, but I would assume this will damage my array? >>> >>> The disk sizes are 1500301910016 bytes and I use 1500250M partition sizes >>> for the array components. Does that sector fall outside my partition, and >>> hence would it be safe to overwrite it with zeros? >>> >>> Also, why did I have a mismatch_cnt? I haven't run another check since I did >>> the repair, as I wanted to fix the pending sector. >>> >>> BTW, I have a 15 drive RAID6. >>> >> >> If you are running RAID6 and it can read from all but two drives then >> it should still be able to calculate whatever would match the >> remaining (presumed good) reads to fill the later two drives. RECENT >> kernels will try to write over failed sectors automatically; and only >> kick the drive if the write fails. >> >> Please provide more information. >> >> Kernel version >> mdadm version >> >> Information about how the source block devices are split up before >> mdadm sees them, and any related messages from the system-log. The >> relevant section should be near the end of a dmesg output when you've >> just completed a check or repair. Your syslog probably already >> captured the same data and stored it elsewhere. > > I thought doing the repair was supposed to fix the issue, but it didn't seem > to touch it. I wonder if it is outside what md sees, but then how would it > have been noticed as unreadable? And is it coincidence that both drives have > the same unreadable sector? > > root@Edna:/home/iain# uname -a > Linux Edna 2.6.28-16-server #57-Ubuntu SMP Wed Nov 11 10:34:04 UTC 2009 > x86_64 GNU/Linux > root@Edna:/home/iain# mdadm -V > mdadm - v2.6.9 - 10th March 2009 > > I paste the end of messages below. There's loads of that all the way through > doing the repair so I'm not sure how to filter out the useful bits. > > > Iain > [...] Hi Iain, the "Current_pending_sectors" is a smart attribute which gets incremented during online (reading and writing sectors) AND offline drive scanning (also called SMART Data Collection), when the drive finds out a sector cannot be correctly read at the first try (offline data collection) or after applying various error-correction techniques. The easiest way to get rid of this problem: dd a sector of zeros onto the broken sector, then fail the drive, re-add it. Now wait until the resync is done. The fact I'm not sure about is: should one fail and re-add both drives at once? As by that the redundancy would get lost... Speaking about redundancy: our rule of thumb (at xtivate.de) is "each 4 drives need one redundancy" - so a redundancy of 2 with 15 drives is kind of playing with your luck... Good luck, Stefan -- 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
