This objective talks about the service dependencies that might directly impact your design decisions. These can be anything for instance App/DB and Webserver are required to run a full fledged web application. In order to host a Virtual Machine, you need ESX/ESXi hosts, Network, Storage etc…
Let us look at a very common example of Service dependencies. In an Active Directory domain there are so many components dependent on each, for ex.
- In order for Exchange Server to function properly it needs Active Directory to be up and running all the time
- If the clients need to acquire the IP address from DHCP Server then the DHCP service should be running all the time
Upstream and Downstream Relationship (from Vmware white paper):
Everything that happens downstream can have an effect on upstream items. For example, if the webserver crashes, the website upstream is affected and goes down. Neither the operating system, nor the cluster are affected, as this are downstream relationships. To memorize this, you could think of a house. The roof is “up” while basement is “down”. If you break down the basement, the roof upstream” also collapses
This objective also talks about Automated Application discovery which helps in mapping the application dependency. There are 3 types of Discovery methods:
Active Discovery, which discovers the inventory components like Application, App Infra, Host and App usage on a regular basis which may cause huge burden on the network bandwidth
Passive Discovery, provides more of the relationship data. By connecting to core Span, port mirroring on network switches it can collects the Network hosts and servers, and their communications and connections, and what services and protocols are being exchanged at what time. But this still requires additional skills to collect the raw data and compile it in a readable format
Discovery Analytics, a combination of Active and Passive Discovery methods which performs a deep-packet analysis of observed traffic and help to establish the relationship between Active & Passive discoveries.
VMware offers a product called VMware vCenter Application Discovery Manager which can assist to discover and draw down these relationships which is termed as a Hybrid discovery method