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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:

    console 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.

  2. To increase the number of files that can be cached, execute the following command:

    console 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.

  3. Execute the following command to enable samba specific metadata caching:

    console gluster volume set <volname> cache-samba-metadata on

  4. 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: console gluster volume set <volname> xattr-cache-list "comma separated xattr list" Eg: console 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

console gluster volume set <VOLNAME> performance.readdir-ahead on gluster volume set <VOLNAME> performance.parallel-readdir on

File/Directory Create Performance

  • Enable nl-cache

console 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.