CAM performance: meaning of Cache% value

hbeck001

    Hello,

     

    what's the meaning of the "Cache %" Value retrieved via CAM (either WebUI or sscs)? I've got two sources and both state different meaning:

     

    • First source, a knowledge base howto from oracle support says the following:

     

    CACHE% Cache Hit Percentage

    Sun Storage Common Array Manager (CAM): How to Collect Performance Data for Sun Storage Arrays (Doc ID 1003966.1)

    (https://support.oracle.com/epmos/faces/DocContentDisplay?id=1003966.1)

     

    • Second source, the CAM manual says something different:

    Cache Hit % The percentage of cache that is affected by the performance statistics data

    Sun StorageTek ™ Array Administration Guide https://docs.oracle.com/cd/E19377-01/821-0966-10/821-0966-10.pdf

     

    While the first quote sounds reasonable for a storage system, the second one really makes me kind of nervous. Does collecting performance data eat up the cache memory that's otherwise used for "real" data? I've got max. values of 80% and higher here!

     

    Any clarification is appreciated.

     

    cheers

    Hans-Jürgen