On 1/25/2013 5:14 AM, Roman Mamedov wrote: > Hello, > > Recently there has been some talk on this list, about probability of seeing an > URE during a RAID5 rebuild on modern large (e.g. 2TB) drives. > > I would like to ask for some advice of what would be the best way to proceed > when such an URE is encountered. This is mostly theoretical, no real situation > at hand at the moment. > > As I understand, a RAID5 that is being resized or rebuilt, has no redundancy; > it is essentially as reliable as a RAID0 of total members-1, or even less. > > So on an unreadable sector that mdadm needs to read (because it has no > redundancy to recover it from), mdadm will: > > - mark the corresponding array member as "failed"; > - mark the one that was being rebuilt/resized onto as "spare"; > - and the whole array as down and "not enough members to start the array". > > Let's assume only a couple of sectors on that member were unreadable, and then > their readability was restored (either by drive replacement or by overwriting > them to making the drive remap), and I would be okay with losing data that was > in those sectors. > > What would be the best way to proceed from there? The best way? Use RAID6 and avoid the situation entirely. "An ounce of prevention is worth a pound of cure", as they say. -- Stan -- 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
