
340 Large Scale and Big Data
t
Client
5
4
3
2
1
R1
If (R1, R2, and R3 are consistent) then 6,
while if R3 is out of data then
Upon arrival of R1 and R2, if they are consistent then 4
If they are not consistent and R1 has the most recent data then 4 and 4a
Upon arrival of R3, if it is not consistent with the most recent data then another 4.a
3. Check requested data
4a
the out-of-date
replicas
2.
2.
Send direct
read request to quorum
replicas (1,2) and wait
their response
2a.
Background read
repair request
1. Issue
read request
4. Response
with R1
R2
R3
6
5
4
3
2
1
6
R1
Strong consistency in Cassandra Eventual consistency in Cassandra
R2
R3
5
3. Check requested data ...