There are many virtual machines (VM) templates that are created in the vSphere for each datastore, i.e. sc-<GUID> / datastore-<ID>. These templates are uploaded multiple times.
BOSH cpi [1] copies the stemcells [2] for datastore locality reasons. In other words, the stemcells are then located closer to where the VMs will reside when cloning them.
Please refer to the following for further information:
https://bosh.io/docs/bosh-components.html#cpi
http://bosh.io/docs/understanding-bosh.html
+Environment:Pivotal Cloud Foundry® Ops Manager (vSphere) versions 1.6.x and 1.7.x