Administrator’s Command Line Guide

Chapter 4. Monitoring Storage Cluster
used for storing user data. Once this space runs out, no data can be written to the cluster.
To better understand how allocatable disk space is calculated, let us consider the following example:
• The cluster has 3 chunk servers. The first chunk server has 200 GB of disk space, the second one — 500
GB, and the third one — 1 TB.
• The default replication factor of 3 is used in the cluster, meaning that each data chunk must have 3
replicas stored on three different chunk servers.
In this example, the available disk space will equal 200 GB, that is, set to the amount of disk space on the
smallest chunk server:
# vstorage -c stor1 top
connected to MDS#1
Cluster 'stor1': healthy
Space: [OK] allocatable 180GB of 200GB, free 1.6TB of 1.7TB
...
This is explained by the fact that in this cluster configuration each server is set to store one replica for each
data chunk. So once the disk space on the smallest chunk server (200 GB) runs out, no more chunks in the
cluster can be created until a new chunk server is added or the replication factor is decreased.
If you now change the replication factor to 2, the vstorage top command will report the available disk space
as 700 GB:
48