@Override
  public AmbryDisk getDiskId() {
    return disk;
  }
Instantiate a disk-backed AmbryReplica instance.
@param clusterMapConfig the {@link ClusterMapConfig} to use.
@param partition the {@link AmbryPartition} of which this is a replica.
@param disk the {@link AmbryDisk} on which this replica resides.
@param isReplicaStopped whether this replica is stopped or not.
@param capacityBytes the capacity in bytes for this replica.
@param replicaSealStatus {@link ReplicaSealStatus} of the replica.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/AmbryServerReplica.java