So I'm somewhat familiar with NFS and ilk, and I realize that NFS 4 is adding a host of new features, when I stumble onto pNFS. It appears to be "parallel" NFS storage, but the diagrams and explanations that I'm getting are about as clear as looking through a greasy Pyrex dish. It also appears that it will "go live" sometime in 2010.
So, I was wondering the following questions:
- Just what does the "parallel" stand for? Parallel I/O? Access? Parallelism? There are several different connotations.
- Is it similar in concept to OpenAFS file services or Windows DFS?
- Does it provide redundant storage? (i.e. spreads out copies of data between servers)?
- There is mention of an object store. Is there a new API that will make this available? Or will this just use existing filesystem semantics to read/write objects?
- There is mention of block storage. Will this allow me to cluster a drive with other clients (i.e. shared filesystem)? And does this imply that I can have my block device on server A servicing multiple clients B and C via pNFS? While you can share a physical disk with iSCSI, this would certainly provide the "missing layer" (filesystem)...
- It appears to use a metadata server similar to CXFS, i.e. there is a separately maintained metadata server that determines what client receives access to what data. Is this restricted to a single metadata server, or can I have some redundancy and load-balancing here as well with multiple servers?