cluster in Hadoop.
An cluster is group of process (generally one machine per process) called node where you will find two kind of nodes:
Additionally, you will have certainly edge nodes that hosts the client application (no services).
Computer - Capacity Planning (Sizing) for a cluster
It depends mostly on how Hadoop is used.
<MATH> \text{Permanent Storage} = 2 . \text{Data Size} = 2 . 10TB = 20 TB \\ \text{Blocks} = 2 . \frac{\text{Data Size}}{\text{block Size}} = 2 . \frac{10000000}{128} = 156,250 </MATH>
<MATH> \text{Temporary Storage} = 2 . \text{Data Size} = 2 . 10TB = 20 TB \\ </MATH>