Explain how Coda provides fault tolerance.

Question

What will be an ideal response?

Answer 1

Coda introduces the notion of volumes.A volume is a logical piece of the file system,
but it is replicated physically across multiple file servers. Servers that hold the same volume
are known as a volume storage group (VSG).Although the multiple servers are transparent
to users, the Venus process on each client periodically probes the VSGs of each of its volumes.
The members of the VSG with which the client can communicate are known collectively
as the client’s available volume storage group (AVSG). Coda uses AVSGs to
implement fault tolerance.When a client process tries to read a file, its request is directed to
the local VFS. If the file is not in the cache,Venus contacts a member of the AVSG known as
the preferred server (PS), which may be designated randomly. If the PS, or any member of
the AVSG, crashes, the client can still operate, because the client can get files from other volumes
in AVSG.