DSM Review, NFS, AFS

Readings

• Jelica Protic et al., "Distributed Shared Memory: Concepts and Systems" (1996)
  This paper reviews work in the area of distributed shared memory.

• Russel Sandberg et al., "Design and Implementation of the Sun Network Filesystem" (1985)
  This is the original NFS paper.

• John H. Howard et al., "Scale and Performance in a Distributed File System" (1988)
  This paper describes AFS and compares it to NFS.

Questions

For the Protic paper, consider the following:

1. What were the major problems addressed in DSM research following Kai Li's dissertation?
2. Did these advances change the scope of environments and problems appropriate for DSM?
3. Why aren't DSM systems commonly in use today?

For the NFS and AFS papers, consider these questions:

1. What were the key design goals of NFS and AFS?
2. How well did they achieve their goals?
3. What are their limitations?
4. How suitable are NFS and AFS in modern small networks? Enterprise networks? Internet-scale applications? Why?

In Class Notes

Goals of NFS and AFS

NFS

• Remote access like local access
• Scale to ~50 clients
• Portability
• Lightweight

AFS

• Remote access like local access
• Scale to 5000 - 10000 hosts
• Portability (POSIX)

Differences

NFS

1. NFS does a system call for every read/write
2. NFS can operate with diskless clients
3. Lightweight clients
4. Files are up-to-date, can be inconsistent
5. Trusted clients

AFS

1. AFS does a system call only on retrieving and storing a file
2. AFS assumes clients have a hard disk
3. Heavier-weight client
4. Files may be stale, but data is consistent
5. Untrusted clients

Aside: Kerberos for Dummies

1. Client Identification:    <client> ==> <kerberos> 
2. Client Request Ticket:    <client> <== <kerberos>
3. Authenticate with Ticket: <client> ==> <server>