As indicated by @StefanosM running a MSDP server on the master is not a good idea (there are occasions where it is necessary, but in general avoid doing it). On the Flex as you have correctly read, it is not possible to create any storage pools on a master server instance, so you would need to have both a master and media server to run NetBackup from the Flex. The master of course could be run elsewhere.
nice, thanks for the reply guys , but looks that when you create Master everything runs as expected and instance created , but when you try to create media server always get different errors such as :
Failed to obtained host ID-based certificate
Failed to determine CA type of the NetBackup domain
CA certificate fingerprint mismatch
this three new setups run with the same CA and i get that CA from master server that create before
its really annoying because its just a "simple setup"
You are right, the correct way is to install 2 instances, one for master and a second for MSDP. I have deployed them several times with no issues. I usually copy the CA SHA-1 fingerprint from the master details in flex console. And I am afraid that for the certificate, if you have tried to deploy it several times you should create a reissue token on the administration console to recertificate the new instance.
Also, regarding best practices, you should check this white paper, there are some rules you should take care with flex deployment:
because that was new installation i delete the master and install again with separate media and looks that was the best solution, btw thanks for the white paper will be helpful for later installations