This is a features present on the SDRS Configuration settings under advance settings.
vCenter server 7.X
vCenter server 8.0
* This is feature which makes sure to keep all the vmdk together on a single datastore, so when you will create a new VM and deployed disk will be assigned automatically to one dedicated datastore that SDRS algorithm will decide.
* Even when you disable the SDRS from the disk setting while creating a new disk, that particular datastore will only get selected unless you uncheck the box " keep vmdk together" on the SDRS advance settings.