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Performance tuning

Enable Metadata cache

Metadata caching improves performance in almost all the workloads, except for use cases with most of the workload accessing a file sumultaneously from multiple clients. 1. Execute the following command to enable metadata caching and cache invalidation: # gluster volume set <volname> group metadata-cache This group command enables caching of stat and xattr information of a file or directory. The caching is refreshed every 10 min, and cache-invalidation is enabled to ensure cache consistency.

  1. To increase the number of files that can be cached, execute the following command: # gluster volume set <volname> network.inode-lru-limit <n> n, is set to 50000. It can be increased if the number of active files in the volume is very high. Increasing this number increases the memory footprint of the brick processes.

  2. Execute the following command to enable samba specific metadata caching: # gluster volume set <volname> cache-samba-metadata on

  3. By default, some xattrs are cached by gluster like: capability xattrs, ima xattrs ACLs, etc. If there are any other xattrs that are used by the application using the Gluster storage, execute the following command to add these xattrs to the metadata cache list: # gluster volume set <volname> xattr-cache-list "comma separated xattr list" Eg: # gluster volume set <volname> xattr-cache-list "*,user.swift.metadata"

Directory operations

Along with enabling the metadata caching, the following options can be set to increase performance of directory operations:

### Directory listing Performance:

  • Enable parallel-readdir # gluster volume set <VOLNAME> performance.readdir-ahead on # gluster volume set <VOLNAME> performance.parallel-readdir on

### File/Directory Create Performance

  • Enable nl-cache # gluster volume set <volname> group nl-cache # gluster volume set <volname> nl-cache-positive-entry on

The above command also enables cache invalidation and increases the timeout to 10 minutes

Small file Read operations

For use cases with dominant small file reads, enable the following options

# gluster volume set <volname> performance.cache-invalidation on
# gluster volume set <volname> features.cache-invalidation on
# gluster volume set <volname> performance.qr-cache-timeout 600 --> 10 min recommended setting
# gluster volume set <volname> cache-invalidation-timeout 600 --> 10 min recommended setting

This command enables caching of the content of small file, in the client cache. Enabling cache invalidation ensures cache consistency.

The total cache size can be set using

# gluster volume set <volname> cache-size <size>

By default, the files with size <=64KB are cached. To change this value:

# gluster volume set <volname> performance.cache-max-file-size <size>

Note that the size arguments use SI unit suffixes, e.g. 64KB or 2MB.