Translators/performance/readahead

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Translator performance/readahead

read-ahead pre-fetches a sequence of blocks in advance based on its predictions. When your application is busy crunching the data it has read, GlusterFS can pre-read the next batch of data and keep it ready to make consecutive reads faster. Additionally, the translator also behaves as a read-aggregator, that is, smaller I/O read operations are combined into fewer larger read operations internally to reduce network and disk load.

volume readahead
  type performance/read-ahead
  option page-count 4           # 2 is default option
  option force-atime-update off # default is off
  subvolumes <x>
end-volume

page-size

The page size in which read-ahead breaks up read requests from the server. The default value is 128KB.

page-count

The maximum number of blocks to pre-fetch. This maximum value is reached only when the read pattern is sequential.

force-atime-update

Keep the atime of the file up to date. The default is off (equivalent to mount -o noatime).

NOTE: This translator is best utilized with IB-verbs transport or with 10GbE interface. With FastEthernet and the GbE interface, without read-ahead, you can achieve link-max throughput.

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