NFS/Kerberos

Our user-data is stored in /export/users on artificial-flavours in a RAID 1 software array running on two 400 GB SATA disks. We export /users via NFSv3 and NFSv4. All of our systems NFSv4 mount /users. We have also explored additional methods for replicating user-data, listed below.

NFS

NFSv3 has been in long standing use by the CSC as well as almost everyone else on the planet. NFSv4 mounts of /users are currently in the works to CSCF. Unfortunatedly NFS has a number of problems. Clients become desperately unhappy when disconnected from the NFS server. Also previous to NFSv4 there was no way to client side cache resulting in poor preformance with large files such as virtual machine hard drives (note: caching has yet to implemented in the CSC).

Coda

Coda is a network filesystem explored several times by the CSC. Unfortunately, coda is a one-way ticket to madness for our users and systems administrators.

DRBD

In our traditional NFS setup the filesytems are backup-ed only through RAID1 on the NFS server. If the NFS server (caffeine) goes down all the CSC systems become desperately unhappy. A proposed way to solve this problem is with network replicated block devices which are traditionally used in clustering systems. DRBD is a network block device system we used for a little while (until it exploded). It is much like network RAID1. Unfortunately, it only supports exporting the device to nodes that are actually replicating it, not clients.

GNBD

GNBD is similar to DRBD but supports clients. It requires integration with fencing.