P4L2 - Distributed File Systems Flashcards
T/F: Modern operating systems export a high-level filesystem interface to abstract all of the different types of storage devices present on a machine
True
What is a Distributed Filesystem
Environments that involve multiple machines for the delivery of the filesystem service
What is the replicated system DFS model
All files are replicated and available on every sever machine
What are the benefits of the replicated system DFS model
- Fault Tolerant
2. Highly Available
What is the partitioned DFS model
Each server holds only some subset of the total files
What are the benefits of the partitioned DFS model?
- Scalable
T/F: It’s uncommon to see a DFS that utilizes both partitioning and replication
False
What is the 3rd alternative to partitioned/replicated DFS models?
Files stored and served from all machines. All systems are peers
A _____ server keeps no notion of which files/blocks are being accessed, which operations are being performed, how many clients are accessing how many files
stateless
In a stateless server, every request must be _______
self-contained
T/F: Stateless servers can be used with models that rely on caching?
False! Without state, we CANNOT achieve consistency management
What are some benefits of stateless server?
- Since there is no state on the server, there is no CPU/memory utilization required to manage that state
- Design is very resilient
A _____ server maintains information about the clients in the system, which files are being accessed, which types of accesses are being performed, which clients have a file cached, which clients have read/written the file
stateful
T/F: Stateful servers can be used with caching models
True
Describe session semantics
Client writes back whatever data was modified on CLOSE. Whenever a client needs to open a file, the cache is skipped
T/F: Session semantics allow a client to be potentially reading from a stale file?
True!
In what scenario is session semantics a poor choice?
Situations were clients want to concurrently share a file
Describe periodic update
In order to avoid long periods of inconsistency, the client may write back changes periodically to the server
T/F: It is not uncommon to adopt one type of semantics of files and one for directories
True
In a ____ _____ ____ clients access files across the network
Networking file system (NFS)
What is responsible for determining if a file belongs to the local file system or whether the request needs to be pushed to the NFS client?
The VFS layer (Virtual File system)
The NFS client interacts with the NFS server via ____
RPC
When an open request comes to an NFS server, it will create a ____ ____
file handle
What is the purpose of a file handle?
It is used in NFS to contain information about the server machine as well as information about a file
NFSv3 is ____ while NFSv4 is ______
stateless
stateful
For files that are not accessed concurrently what type of semantics does NFS employ?
Session semantics
T/F: NFS does not support periodic updates
False!
According to “Caching in the Sprite Network File System” what percent of file access are writes?
33%
According to “Caching in the Sprite Network File System” what percent of files were open less than half a second
75%
According to “Caching in the Sprite Network File System” what percent of new data was deleted within 30 seconds
20-30%
