On 2010-07-04 20:29, Mario 'BitKoenig' Holbe wrote: > Niobos <niobos@xxxxxxxxxxxxxxx> wrote: >> I'm running cmp on an active RAID. My guess is that this cause a large >> number of false positives: cmp reading both members at a different time, >> and hence reading a different version. That was the main reason to ask >> for another way to get the mismatching blocks through the raid-layer. > On high-frequent changes this can unfortunately happen with RAID1 due to > the handling of dirty pages (there's a thread back in 2k6 here on the > list where Heinz Mauelshagen explained this quite nice - somewhere below > the Subject: No syncing after crash. Is this a software raid bug?). > I didn't notice it anymore since >2.6.26, so I thought it was fixed, but > this could also be because the probability shrunk due to new hardware. > >> I'm running cmp on an active RAID. My guess is that this cause a large >> number of false positives: cmp reading both members at a different time, >> and hence reading a different version. That was the main reason to ask > > Not very likely unless your filesystem is under very high load. To be > more specific: I did cmp -l my mirrors regularly before the "check" > sync_action had been developed (and still do it from time to time - > never trust... :)) and never experienced such things. I just did 5 cmp's sequentially, with minutes in between them: -rw-r--r-- 1 root root 15016204 2010-07-05 09:18 sd[ab]1.1.diff -rw-r--r-- 1 root root 21404544 2010-07-05 09:49 sd[ab]1.2.diff -rw-r--r-- 1 root root 40538120 2010-07-05 09:54 sd[ab]1.3.diff -rw-r--r-- 1 root root 415879184 2010-07-05 10:39 sd[ab]1.4.diff -rw-r--r-- 1 root root 24811696 2010-07-05 11:45 sd[ab]1.5.diff >From the output-size alone, one can see that something is not working as described. There are millions of bytes that mismatched at 10:39, that magically were "fixed" an hour later... I'm not sure how to quantify "very heavy filesystem load", but I don't thing it is. thanks, Niobos -- 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
