Hi! I have been reading the "Clarifications about check/repair, i.e. RAID SCRUBBING" thread, and there were some answers which were still slightly unclear to me, and I'd like to get a bit more clarification. This is all in reference to the /sys/block/md0/md/sync_action setting. Neil Brown wrote: > 'check' just reads everything and doesn't trigger any writes unless a > read error is detected, in which case the normally read-error handing > kicks in. So it can be useful on a read-only array. > > 'repair' does that same but when it finds an inconsistency is corrects > it by writing something. > If any raid personality had not be taught to specifically understand > 'check', then a 'check' run would effect a 'repair'. I think 2.6.17 > will have all personalities doing the right thing. > > check doesn't keep a record of problems, just a count. 'repair' will > reprocess the whole array. What exactly is the normal read-error handling behavior that is invoked when 'check' detects a read error, especially in regards to raid level 5? Also, why exactly is 'check' useful on a read-only array? Does this mean on an array which has 'array_state' set to 'readonly'? In this case, I'm guessing this is designed to be useful in repairing a dirty and degraded array, correct? Lastly, under which mounted conditions are 'check' and 'repair' safe/useful? Can I run both on a read-write mounted partition? Should they be read-only, or totally unmounted? I'm assuming since resyncs can occur while the overlying fs is mounted read-write, that it is both safe and useful to both 'check' and 'repair' while the fs is mounted read-write as well, but I don't see this mentioned explicitly anywhere. Please CC: me, as I'm not on the list. Thank you very much! TJ Harrell - 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
