On 15.11.2013, at 12:13, Nick Morrison <nick@nick.on.net> wrote: > .. and md5sum gave me a third, different, result. > > It seems as if the data read from the snapshot is changing. More tests. I created a snapshot using # lvcreate -pr -L 2G -s -n test-snapshot /dev/VolGroup00/LogVol00 Then I ran: # md5sum /dev/VolGroup00/test-snapshot ... three times. test-snapshot is a read-only snapshot of the / volume, which is about 265G. One one server, each time, I got a different md5sum. Generally a bad result. However: on the other server, I got the same md5sum result on the first and third runs, but a different result on the second. Curious. I'm getting no interesting messages in dmesg during the reads. Is it likely that we have a fault at a lower level than LVM's snapshot code here? [root@server-01:/backup/test]# cat nohup.out Checking md5sum of /dev/VolGroup00/test-dump multiple times. Pass 1 started Fri Nov 29 11:46:56 CET 2013 103fa0cc0351836598866423fabcfb6b /dev/VolGroup00/test-dump real 34m31.006s user 15m15.252s sys 6m48.961s Pass 2 started Fri Nov 29 12:21:28 CET 2013 2d37fce8eea493eb4600f1593b9da825 /dev/VolGroup00/test-dump real 34m24.818s user 15m11.098s sys 6m28.567s Pass 3 started Fri Nov 29 12:55:52 CET 2013 4f6940a672115b896cea5220ba8bde7c /dev/VolGroup00/test-dump real 35m13.079s user 15m15.016s sys 6m19.312s Complete at Fri Nov 29 13:31:05 CET 2013 [root@server-01:/backup/test]# Other server: [root@server-02:/backup/test]# cat nohup.out Checking md5sum of /dev/VolGroup00/test-dump multiple times. Pass 1 started Fri Nov 29 11:47:04 CET 2013 de7f4847be8dd3019ee2a690f48c6397 /dev/VolGroup00/test-dump real 29m34.334s user 14m49.219s sys 6m33.685s Pass 2 started Fri Nov 29 12:16:38 CET 2013 363ee32c1bb5da6eb9754b0d6de79180 /dev/VolGroup00/test-dump real 29m24.910s user 14m40.705s sys 6m44.806s Pass 3 started Fri Nov 29 12:46:03 CET 2013 de7f4847be8dd3019ee2a690f48c6397 /dev/VolGroup00/test-dump real 29m20.927s user 14m40.441s sys 6m46.865s Complete at Fri Nov 29 13:15:24 CET 2013 [root@server-02:/backup/test]#
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