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Diffstat (limited to 'src/seastar/doc/io-properties-file.md')
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diff --git a/src/seastar/doc/io-properties-file.md b/src/seastar/doc/io-properties-file.md new file mode 100644 index 000000000..750319077 --- /dev/null +++ b/src/seastar/doc/io-properties-file.md @@ -0,0 +1,41 @@ +# Specifying the I/O properties of a system + +The I/O properties of a system can be specified as a YAML string, by +using the option --io-properties, or as a YAML file with the option +--io-properties-file. + +The expected format starts with a map of sections at the top level. +Currently only `disks` is supported. + +## The disks section + +Inside the `disks` section, the user can specify a list of mount points. + +For each mount point, 4 properties have to be specified (none are +optional): + +* `read_iops`: read IOPS speed of the device +* `read_bandwidth`: read bandwidth speed of the device +* `write_iops`: write IOPS speed of the device +* `write_bandwidth`: write bandwidth speed of the device + + +Additionally the following optional properties can be added: + +* `read_saturation_length`: read buffer length to saturate the device throughput +* `write_saturation_length`: write buffer length to saturate the device throughput + +Those quantities can be specified in raw form, or followed with a +suffix (k, M, G, or T). + +Example: + +``` +disks: + - mountpoint: /var/lib/some_seastar_app + read_iops: 95000 + read_bandwidth: 545M + write_iops: 85000 + write_bandwidth: 510M + write_saturation_length: 64k +``` |