Subject: [nfsv4] writeverf reply from File Layout DS?

From: Rick Macklem <[email-masked]>
Date: Wed, 1 Feb 2012 22:23:51 -0500 (EST)

Hi,

The following snippet of RFC5661 seems to be clear, for the case
of COMMIT through the MDS:
      If nfl_util & NFL4_UFLG_COMMIT_THRU_MDS is TRUE, then in order to
      maintain the current NFSv4.1 commit and recovery model, the data
      servers MUST return a common writeverf verifier in all WRITE
      responses for a given file layout, and the metadata server's
      COMMIT implementation must return the same writeverf.  The value
      of the writeverf verifier MUST be changed at the metadata server
      or any data server that is referenced in the layout, whenever
      there is a server event that can possibly lead to loss of
      uncommitted data.  The scope of the verifier can be for a file or
      for the entire pNFS server.  It might be more difficult for the
      server to maintain the verifier at the file level, but the benefit
      is that only events that impact a given file will require recovery
      action.

However, I can't find a similar statement for COMMIT through the DS.
(I probably just can't find it, so just tell me to go back to the RFC
 if it's there.;-)

Would I be correct to assume that, for the case of COMMIT through the
DS, that the writeverf will be specific to the DS and the client has
to keep/check a separate one for each DS?

Thanks in advance for help with this. rick