Topic
1 reply Latest Post - ‏2014-07-29T14:14:04Z by chriscanto
TMasteen
TMasteen
279 Posts
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Pinned topic V7000 984003 message

‏2014-07-29T07:03:41Z |

On two different V7000 systems (running 7.2.x.x) we get Warning 984003  I/O group caching was set to synchronous destage and 1 hour later the Informational message 984004 I/O group caching was set to allow asynchronous destage. Always exactly 1 hour between the two messages.

Messages are generated almost every night while there is no load on the system (checked with TPC).

One week ago while one of the two systems was still running 6.4.x.x, we had no messages on that system.

Any ideas?

Thanks.

  • chriscanto
    chriscanto
    274 Posts
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    Re: V7000 984003 message

    ‏2014-07-29T14:14:04Z  in response to TMasteen

    The 1 hour period is the minimum amount of time an SVC/Storwize system needs to have seen good performance from having switched to the synchronous destage mode before logging that is has switched back to the normal async destage mode.  Note that it may well be switching back to async much sooner, but it only logs it after at least 1 hour of clean running has passed, to avoid flooding the event log if the problem is intermittent.

    For the system to go into the synchronous destage mode suggests a cache partition is becoming full.

    If there really is no load on the system when the 984003 event is logged then that sounds like a bug in the 7.2.0 code.  However, I wonder if you might actually have some workload on the system just before that event is logged, and that the workload arrives as a sudden burst, overloading the underlying storage, but because of the sampling period in TPC averaging over several minutes then it doesn't look like much there?

    As the cache component has been totally rewritten in the 7.3 release then I it might not be worth putting much effort into debugging on 7.2 if it's not actually causing any impact.

    Updated on 2014-07-29T14:15:01Z at 2014-07-29T14:15:01Z by chriscanto