Unstable clock

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Hi,

I am looking at the following issue: http://tracker.ceph.com/issues/21375

In summary, during a 'rados bench', impossible latency values (e.g.
9.00648e+07) are suddenly reported. I looked briefly at the code, it
seems CLOCK_REALTIME is used, which means that wall clock changes would
affect this output. This is a VM cluster, so the hypothesis was that the
system's clock was falling behind for some reason, then getting
readjusted (that's the only way I could reproduce the issue), which I
think is quite possible in a virtual environment.

A concern was raised: are there more critical parts of Ceph where a
clock jumping around might interfere with the behavior of the cluster?
It would be good to know if there are any, and maybe prepare for them?

Mohamad
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