To read a replicated file, a client

must also first contact at least half $)$ of the servers plus $1$

$($i$.$e$.,\frac{N}{2}+1$ thus a majority$)$ and get them to send the version

numbers associated with the file;

If the version numbers are

all the same, indicating the file is the most recent version, then can read

the file;

different, then read the file with the newest version number.Referring to PPT of Module $8($e$.$g$.,$ slide No$\mathrm{.}30),$ a legal scheme of the Gifford's Quorum scheme $($voting algorithm$)$ is described as:

where $N_W$ is the write quorum, $N_R$ the read quorum and $N$ the number of replicas.

Suppose a file is replicated on $10$ servers.

List two combinations of write quorum $N_W$ and read quorum $N_R,$ in a form of $(N_W,N_R),$ that are permitted by the voting algorithm.

List three combinations of write quorum $N_W$ and read quorum $N_R,$ in a form of $(N_W,N_R),$ that are not permitted by the voting algorithm, such that one of the combinations violates read$-$write

conflict only, another violates the write$-$write conflicts condition only, and the last one violates both conditions. Briefly explain your answer.

Given a quorum scheme with $N_W=6$ and $N_R=4,$ determine if this scheme qualifies for Gifford's Quorum scheme? Describe a scenario where this scheme may cause issues$/$problems for file

read$/$write operations.