On Tue, Nov 3, 2009 at 4:14 PM, Paul Gilmartin <[email protected]> wrote:

>> This is cheating. Sure, if you assume the operating system has the
>> right time, you just ask there...
>>
> So it's cheating to ask your own OS, but not cheating to ask
> a remote OS?  What if your system lacks network connection?

You just don't simply ask anyone, you ask a complex of synchronized
servers that have a close connection to an trusted source. Experience
shows that sometimes the operator will set the z/VM LPAR TOD offset
not using a reliable source.At that point your System z clock is still
stable, but very wrong.

For Linux on z/VM, the best approach is to make sure z/VM has the
right time at IPL. When your applications really can't afford the
typical drift of a System z, make the hardware steer the LPAR. That
will make all Linux guests have the same clock. Often better than each
trying to sync itself with the outside.

Rob

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