Is one node reliable in Cassandra?

Question

I'm new to Cassandra, In all the tutorials I read, it is mentioned that we have a few nodes in Cassandra architecture because if one has a problem, the others can do it.

Does using only one node put us at risk of data loss?

I mostly worked with relational databases. Using one node is not a problem in RDBMS (except that for some reason the service may not be available but the data is still stored)

My project does not require high availability, only I have very large data and write a lot data, so I chose Cassandra, but I want use it with only one node

Is this a problem for me? Is my data compromised?

Answer 1

Using a single server can result in data loss - even on a relational database since while you might have regular backups, the commit log / redo log is stored on the server disk until archived away from the server. So a failure of the server disk on the server would result in that log being lost and data since the last backup that is held off the server.

Using multiple servers (relational mirror or distributed no-sql such as Cassandra) provides extra resilience as well as reducing the chance of data loss - since there are 2 or more copies.

In a 3 node cluster with a replication factor of 3 on Cassandra, to get the same data loss as the single server scenario would require all 3 servers going down at once and all of them losing their disks (this assumes local disk, if you use a SAN, you lose the benefit.) - this lowers the percentage chance of data loss considerably.