What is an encryption at rest consideration?

A customer is considering a Dell EMC Avamar backup solution. They want to know whether Avamar can provide the security benefit of data encryption for the data stored on Avamar.

What is an encryption at rest consideration?
A . Encryption at rest will incur a server performance penalty
B . Encryption at rest can be changed at any time without incurring a performance penalty
C . Encryption at rest will increase the disk read-only limit from 65% to 80%
D . Encryption at rest cannot be enabled after installation

Answer: A