RPC 41: MDS_STATFS
~~~~~~~~~~~~~~~~~~
[[mds-statfs-rpc]]

MDS_STATFS ('pb_opc' = 41) is an RPC that queries data about the
underlying file system for a given MDT. It's form and use are nearly
identical to the OST_STATFS RPC. Refer to <<ost-statfs-rpc>> for
details. The only differences in MDS_STATFS are that it has a distinct
'pb_opc' value and it carries information about an MDT (instead of an
OST).  An MDT will send regular OST_STATFS RPCs to each OST in order
to keep its information about free space and utilization updated.
That allows the MDS to make more optimal file allocation decisions.

.MDS_STATFS Request Packet Structure
image::mds-statfs-request.png["MDS_STATFS Request Packet Structure",height=50]

//////////////////////////////////////////////////////////////////////
The mds-statfs-request.png diagram resembles this text art:

       MDS_STATFS:
      --request------
      | ptlrpc_body |
      ---------------
//////////////////////////////////////////////////////////////////////

'ptlrpc_body':: RPC descriptor. See <<struct-ptlrpc-body>>.

.MDS_STATFS Reply Packet Structure
image::mds-statfs-reply.png["MDS_STATFS Reply Packet Structure",height=50]

//////////////////////////////////////////////////////////////////////
The mds-statfs-reply.png diagram resembles this text art:

       MDS_STATFS:
      --reply---------------------
      | ptlrpc_body | obd_statfs |
      ----------------------------
//////////////////////////////////////////////////////////////////////

'ptlrpc_body':: RPC descriptor. See <<struct-ptlrpc-body>>.

'obd_statfs':: Statfs information about the target. See
<<struct-obd-statfs>>.