Le 19/11/2013 22:20, Arnold Krille a écrit :
On Tue, 19 Nov 2013 14:29:32 +0100 "FDS | Forensik Data Services"
<[email protected]> wrote:
Just clarifying my understanding of an UpToDate-Status of a DRBD
Resource in Dual Primary Mode on 2 nodes.
Does a MD5-Hash calculation of both resources lead to equal MD5
values?
That depends. Prerequisites:
- Both primaries are unmounted.
- Both primaries are completely synced from the os/fs point of view.
(That is "sync" has been run and thus all write-buffers are cleared.)
Then an md5-hash of the drbd-device on both machines should return the
same. Also md5-hashes of all the underlaying devices should(*) return
the same.
A MD5 match proves everything is ok BUT a mismatch does not always mean
trouble.
There may be harmless differences if the layers above "cut corners" and
modify blocks in memory after they've been sent to DRBD.
RaiserFS and swap memory are known to do this. See "Notes on data
integrity" at http://www.drbd.org/users-guide/re-drbdconf.html for more
examples and details.
Lionel Sausin.
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