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From Apache Wiki <>
Subject [Couchdb Wiki] Update of "Performance" by RandallLeeds
Date Thu, 17 Jun 2010 21:12:12 GMT
Dear Wiki user,

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The "Performance" page has been changed by RandallLeeds.
The comment on this change is: Add information on +A <n> flag.


  If your system does not use PAM, a {{{ulimit}}} command is usually available for use in
a custom script to launch CouchDB with increased resource limits.
  If necessary, feel free to increase this limits as long as your hardware can handle the
+ = Disk and File System Performance =
+ Using faster disks, striped RAID arrays and modern file systems can all speed up your CouchDB
deployment. However, there is one option that can increase the responsiveness of your CouchDB
server when disk performance is a bottleneck. From the erlang documentation for the file module:
+ On operating systems with thread support, it is possible to let file operations be performed
in threads of their own, allowing other Erlang processes to continue executing in parallel
with the file operations. See the command line flag +A in erl(1).}}}
+ Setting this argument to a number greater than zero can keep your CouchDB installation responsive
even during periods of heavy disk utilization. The easiest way to set this option is through
the {{{ERL_FLAGS}}} environment variable. For example, to give Erlang four threads with which
to perform i/o operations add the following to {{{(prefix)/etc/defaults/couchdb}}} (or equivalent):
+ export ERL_FLAGS="+A 4"}}}

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