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In a NDMP restore log, what are inomap cache hits and cache misses?

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ontap-9
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dp
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Applies to

ONTAP 9

Answer

  • In an NDMP restore log, there is a line listing VM inomap cache hits and misses:
(VM inomap  : Cache hits (            56634222), Cache misses (            14994008))
  • The inomap maps the inode numbers from the backup image to the inode numbers on the file system where the data is being restored.
  • The cache is used to speed up this mapping process.
  • Cache hits: This indicates the number of times the requested data was found in the cache. A high number of cache hits typically means that the restore process can proceed more quickly because the necessary inode information is readily available from the cache, reducing the need to read from the slower disk or tape media.
  • Cache misses: This indicates the number of times the requested data was not found in the cache, necessitating a fetch from the underlying storage media. Cache misses can slow down the restore process because the system must retrieve the inode information from the disk or tape, which is slower than accessing the cache.

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