README.md: Add note regarding Direct I/O #226
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The introduction of
ardb-serveralong withrocksdbresulted in using direct I/O. This is configured in the corresponding configuration file.Our tests suggested that direct I/O isn't guaranteed to be available on systems using ZFS (see this issue) or unprivileged LXC containers. The
ardb-serverinstance would crash on startup using the default configuration. Therefore it was necessary to disable this feature.To save people from having to diagnose this, this PR adds a note regarding this issue in the
README.mdfile.Note: An easy way to check if direct I/O is available on a given host is to execute
dd oflag=direct if=/dev/zero of=/tmp/testfile bs=1M count=1and checking the output for errors.