NAS – Ceph or Gluster for Implementing Big NAS

We are planning to build NAS solution which will be primarily used via NFS and CIFS and workloads ranging from various archival application to more “real-time processing”. The NAS will not be used as a block storage for virtual machines, so the access really will always be file oriented.

We are considering primarily two designs and I’d like to kindly ask for any thoughts, views, insights, experiences.

Both designs utilize “distributed storage software at some level”. Both designs would be built from commodity servers and should scale as we grow. Both designs involve virtualization for instantiating "access virtual machines" which will be serving the NFS and CIFS protocol – so in this sense the access layer is decoupled from the data layer itself.

First design is based on a distributed filesystem like Gluster or CephFS. We would deploy this software on those commodity servers and mount the resultant filesystem on the “access virtual machines” and they would be serving the mounted filesystem via NFS/CIFS.

Second design is based on distributed block storage using CEPH. So we would build distributed block storage on those commodity servers, and then, via virtualization (like OpenStack Cinder) we would allocate the block storage into the access VM. Inside the access VM we would deploy ZFS which would aggregate block storage into a single filesystem. And this filesystem would be served via NFS/CIFS from the very same VM.

Any advises and insights highly appreciated. I should also say that we are internally inclined towards the "monster VM" approach due to seemingly simpler architecture (data distribution on block layer rather than on file system layer).

Cheers,
Prema