The SHORTIO functionality was landed in Lustre 2.11, at the same time as DoM, so these features do not currently work together.

It may just be a matter of enabling the OBD_CONNECT_SHORTIO feature flag on the MDS connection, but it may be that more work is needed.

One related possibility is to include DoM file’s dirty data in the close RPC (or conversely a close in the write RPC, whichever makes more sense). That would further reduce the RPC count for small files. Also, since the DoM close will also be updating attributes like atime or mtime/ctime, we may as well write the data at the same time to avoid more disk IO if they are done in separate RPCs.