Distributed Systems

Storage systems are generally categorized by their persistence, including volatile (RAM), non-volatile (HDD/SSD), and stable storage (redundant systems), making all of these valid classifications.

NIS stands for Network Information Service, a directory service protocol used for distributing system configuration data across a network.

NFS stands for Network File System, a distributed file system protocol that allows a user on a client computer to access files over a network.

In Cristian's algorithm for clock synchronization, T0 and T1 are measured using the same local clock to calculate the round-trip time and estimate the offset.

Stateless servers do not maintain client state between requests, so if a client crashes, the server is unaffected because it does not rely on persistent state for that client.

The all-or-nothing property, also known as atomicity, is a fundamental characteristic of transactions in database and distributed systems.

In a two-level directory structure, files are identified by a combination of the user name and the file name. The file name itself is a symbolic name, and the system often maps these to internal identifiers.

WORM is a data storage technology that allows data to be written to a storage medium a single time and prevents the drive from erasing the data.

In a centralized algorithm for mutual exclusion, the coordinator manages requests. A process sends a request to the coordinator and receives a grant, totaling 2 messages per entry.

An immutable object or file is one whose state cannot be modified after it is created. This is a common concept in functional programming and distributed file systems.

A file service is the interface that defines the operations available to clients for accessing and manipulating files within a distributed file system.

Write-through is a caching strategy where data is written to the cache and the underlying storage simultaneously, ensuring consistency between the two.

In a centralized mutual exclusion algorithm, a single process is designated as the coordinator to manage access to the critical section.

Replication improves availability by providing redundant copies, reliability by ensuring data survives failures, and response time by allowing access to local copies.

In Cristian's algorithm, the client requests the time from a time server. The server is passive, as it only responds to requests from clients.

In a perfect clock, the rate of the clock matches the rate of real time, meaning the derivative of clock time with respect to real time is 1.