ceph/src/seastar/doc/io-properties-file.md

   1 # Specifying the I/O properties of a system
   2
   3 The I/O properties of a system can be specified as a YAML string, by
   4 using the option --io-properties, or as a YAML file with the option
   5 --io-properties-file.
   6
   7 The expected format starts with a map of sections at the top level.
   8 Currently only `disks` is supported.
   9
  10 ## The disks section
  11
  12 Inside the `disks` section, the user can specify a list of mount points.
  13
  14 For each mount point, 4 properties have to be specified (none are
  15 optional):
  16
  17 * `read_iops`: read IOPS speed of the device
  18 * `read_bandwidth`: read bandwidth speed of the device
  19 * `write_iops`: write IOPS speed of the device
  20 * `write_bandwidth`: write bandwidth speed of the device
  21
  22
  23 Additionally the following optional properties can be added:
  24
  25 * `read_saturation_length`: read buffer length to saturate the device throughput
  26 * `write_saturation_length`: write buffer length to saturate the device throughput
  27
  28 Those quantities can be specified in raw form, or followed with a
  29 suffix (k, M, G, or T).
  30
  31 Example:
  32
  33 ```
  34 disks:
  35   - mountpoint: /var/lib/some_seastar_app
  36     read_iops: 95000
  37     read_bandwidth: 545M
  38     write_iops: 85000
  39     write_bandwidth: 510M
  40     write_saturation_length: 64k
  41 ```