During OST addition,
1. MDT gets configuration refreshment first.
2. Then MDT get create request from the client, might allocate the object the new OST, then reply to the client.
3. If client does not refresh its configuration yet, then do I/O with the EA, it might get EIO because it does not know the OST.
So it probably needs add version to the config log to avoid this happen.
This happens quite often in cloud environment. though not sure if there is duplicate ticket already.