While deciding on the sizing of hardware required we are primarily looking for
1) Disk Space Required for Machine hosting Data Warehouse
2) RAM on the Machine
3) CPU
This is for ELT method where Data Warehouse and Integration Server would reside on same machine.
(not the ETL, where DW and integration server will be on different machines)
Disk Space: We will need to consider following->
a) What size of master tables and transaction tables we will pull from source system into Data Warehouse that will form Dimensions and Facts.
b) Space would be needed by staging area. We may not pull all the columns of a particular table, we may pull only selective columns so space needed would be less.
c) The tables in source system will be in Normalized form whereas in DW they are demoralized so there would be redundancy and so more space need for them in DW.
d) The dimensions that we create in DW may need to retain history, i.e. SCD implementation so space needed would be more.
e) The indexes created on Dimension and Fact tables would need space.
f) There would be aggregated/ summarized tables and/or MVs over and above leaf level fact tables so space would be needed for them. The number of summary level fact would depend on the levels in dimensions, more the levels in dimensions more summary tables would require. Indexes would be required in summary tables also so would need space.
