You can't assume a disk is losing sectors and failing without running some diagnostics. If you had an improper shutdown (i.e, power loss, not a crash), and disks were writing, then you can get ECC errors. That does not indicate the disk is bad. Of course, you must always have a backup, even if both drives are perfectly fine, RAID1 doesn't protect you from entering rm -rf * tmp instead of rm -rf *.tmp I strongly advise against using Richard's dd if=/dev/zero suggestion. It puts you at risk as you only have one online copy of the data .. unless you have current backup and it can easily do a cold-metal restore. Not worth the risk if you ask me. Enter dd if=/dev/md0 of=/dev/null instead, and it will force parity rebuild. You do this with both disks online in RAID1. Furthermore, you can get report of what blocks were bad. There is likely also a mdadm rescan or mdadm rebuild, but you'd have to look up syntax. They are preferable to using the dd command. Either technique won't technically check all physical blocks on both disks, but they will take you considerably less clock time, and will protect your data. Warning .. A block-level dd read on every block in md0 will not necessarily rebuild parity for all kernels. You probably have to do something to temporarily disable cache, I don't know. Good luck - David @ santools ^com http://www.santools.com/smart/unix/manual (Use a smaller blocksize to dd if you -----Original Message----- From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of Richard Scobie Sent: Friday, April 18, 2008 5:02 PM To: Linux RAID Mailing List Subject: Re: RAID1 == two different ARRAY in scan, and Q on read error corrected Phil Lobbes wrote: ____________________________________________________________ > > Apr 15 11:07:14 kernel: raid1: sdc1: rescheduling sector 517365296 > Apr 15 11:07:54 kernel: raid1:md0: read error corrected (8 sectors at 517365296 on sdc1) > Apr 15 11:07:54 kernel: raid1: sdc1: redirecting sector 517365296 to another mirror > Apr 15 11:08:32 kernel: raid1: sdc1: rescheduling sector 517365472 > Apr 15 11:09:09 kernel: raid1:md0: read error corrected (8 sectors at 517365472 on sdc1) > Apr 15 11:09:09 kernel: raid1: sdc1: redirecting sector 517365472 to another mirror These entries, > Apr 18 14:01:45 smartd[2104]: Device: /dev/sdc, 3 Currently unreadable (pending) sectors and this, indicate that sdc is losing sectors, so you probably want a backup of the array. Depending on how important the array is you could fail and remove sdc from the array, dd if=/dev/zero of=/dev/sdc bs=1M and re-add it back. It may then be fine for some time, but if it continues to gather pending sectors in the short term, it is probably dying. Otherwise just replace it with a new one. Regards, Richard -- 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 -- 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
