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What are the counters from the flexscale-access output and how does it work?

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Applies to

  • ONTAP 9
  • NetApp recommends using the iterative form of the command with a preset for the Flash Cache counters.
  • This provides output every 5 seconds of per-second data rates for the most critical counters
:>stats show -p flexscale-access
 
 

Here are the definitions for those counters:

·      Cache Usage: How much data is currently storedin the module or modules.

·      Hit: The 4kB disk block cache hit per second.

·      Meta: The 4kB metadata disk block cache hit persecond.

·      Miss: The 4kB disk block cache missed per second.

·      Hit: The percentage of total hit/miss

·      Evict: The 4kB disk blocks evicted (leavingcache because of set collision) from the cache per second.

·      Inval: The 4kB disk blocks invalidated (leavingcache because of overwrite or making room) from the cache per second.

·      Insert: The 4kB disk blocks inserted into thecache per second.

·      Reads Chain: The number of read I/O chains persecond.

·      Reads Blocks: The number of 4kB disk blocks readper second.

·      Writes Chain: The number of write I/O chains persecond.

·      Writes Blocks: The number of 4kB disk blockswritten per second.

·      Disk Reads Replaced: The number of reads thatwould have gone to disk that were replaced by the cache per second.

 

  • In this output, the most important data are the hit rate and the number of disk reads replaced. It might also be useful to capture sysstat data to understand the amount of workload on the system.

 

Additional Information

  • For more information, refer below document (page15):

Flash Cache Best Practice Guide 

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