Add documentation for GPFS metric

collectors/gpfsMetric.md

@@ -0,0 +1,30 @@
+## `gpfs` collector
+
+```json
+  "ibstat": {
+    "mmpmon_path": "/path/to/mmpmon",
+    "exclude_filesystem": [
+      "fs1"
+    ]
+  }
+```
+
+The `gpfs` collector uses the `mmpmon` command to read performance metrics for
+GPFS / IBM Spectrum Scale filesystems.
+
+The reported filesystems can be filtered with the `exclude_filesystem` option
+in the configuration.
+
+The path to the `mmpmon` command can be configured with the `mmpmon_path` option
+in the configuration.
+
+Metrics:
+* `bytes_read`
+* `gpfs_bytes_written`
+* `gpfs_num_opens`
+* `gpfs_num_closes`
+* `gpfs_num_reads`
+* `gpfs_num_readdirs`
+* `gpfs_num_inode_updates`
+
+The collector adds a `filesystem` tag to all metrics