Talk:Untrusted Distributed Storage

Group 1

Pond:
1) Why use Java?
2) How was the inner-ring chosen?
3) How big was the prototype able to scale?

Farsite:
1) What is convergence cryptography?
2) What are the advantages/disadvantages of not locking the directory name of an open file handle?
3) What assumptions did they make about concurrency in the system and how did they plan to handle it?

Retro:
1) Why did this never move beyond a research project?
2) (in lessons learned) networking turned out to be the limiting factor over disk space.
Why had they assumed that networking wouldn't be an issue?
3) What planned goals did they achieve?

Group 2

OceanStore

1. What was the purpose of introspection in terms of nomadic data?
2. How does the less-reliable-but-faster probabalistic lookup work?
3. What is a Bloom filter and how is it used in OceanStore?

FarSite

1. Farsite was desgined to look like NTFS. How do Farsite's semantics differ from NTFS?
2. How is the content lease system similar to lease systems in distributed systems we've already seen, and which is most similar?
3. What is the scope of Farsite? Could it work as a world wide filesystem like OceanStore.

Retro

1. How did the lease system change between planning and implementation?
2. What was the programming model used in the implementation of Farsite?
3. What was the biggest disadvantage to the implementation?

Group 3 - Farsite

OceanStore

1) What is convergence cryptography?

Ans. The file key is used to encrypt the hashes rather than to encrypt the file blocks directly.

2) What are the advantages/disadvantages of not locking the directory name of an open file handle?

Ans. Advantages - The results of directory rename operations are not propagated synchronously to all descendent directory groups during the rename operation, because this would unacceptably retard the rename operation, particularly for directories near the root of the namespace tree.

Disadvantages- because they used lazy propagation, other users wouldn’t see the name immediately, also more then one user can change the name at the same time.

3) What assumptions did they make about concurrency in the system and how did they plan to handle it?

Ans. The authors assume that no files are both read by many users and also frequently updated by at least one user. How did they handle it? There are four classes of leases in Farsite: content leases, name leases,mode leases, and access leases.

Retro

1)Whats is the main target environment for farsite?

Ans. The target was governments and universities environments

2) What are the 3 different type of certificates? And what are their purposes?

Ans. Namespace certificates – associated the root of a file system namespace with a set of machines that manage the root metadata.

User certificates - associates a user with his personal public key, so that the user identity can be validated for access control.

Machine certificates - associates a machine with its own public key, which is used for establishing the validity of the machine as a physically unique resource

3) What is convergence encryption?

Ans. The file key is used to encrypt the hashes rather than to encrypt the file blocks directly.

Ponds

1) Farsite was designed to look like NTFS. How do Farsite’s semantics differ from NTFS?

Ans. First: Farsite has multi reader single writer policy. Additional attempts to read an open file will receive a handle to a snapshot of the file, it will not change to reflect updates by remote writers. An application can query the Farsite client to find out whether it has a snapshot handle or a true file handle, but this is not part of NTFS semantics.

Second: NTFS does not allow a directory to be renamed if there is an open handle on a file in the directory or in any of its descendents. Thus, Farsite instead implements the Unixlike semantics of not name-locking an open file's path.

2) How is the content lease system similar to lease systems in distributed systems we’ve already seen and which is most similar.

3) What is the scope of Farsite? Could it work as a World Wide file system like OceanStore.

Ans. Farsites main scope was that of a univertisy, governement or large company. Analysis points to a scale of approximately 10^5 machines whereas OceanStore is around 10^10

Group 4 - Farsite Retrospective

Some questions were received by paper so they are put here as well as "FROM <GROUP>"

TO OceanStore

1. What is their business model?
2. What is introspective and what are its many applications?¬
3. What are the advantages of using a “Version Control System” over a typical file system model?

TO Pond

1. What is Tapestry and how does it work?
2. How did they meet the expectations of the original OceanStore paper and vision? (i.e. how did they solve design problems)
3. What is the difference between the primary and secondary replicas?

TO FARSITE

1. What was the target environment for FARSITE?
2. What were the three different types of certificates and what were their purposes?
3. What is convergent encryption?

FROM Pond

1. How did the lease system change between planning and implementation?
2. What are the programming models used in the implementation?
3. What was the biggest disadvantage to their implementation?

From FARSITE(?)

1. What are the trends in technology that justify FARSITE?
2. Were the team members familiar with windows SIS driver?
3. What's WebDAV?