it's all about the Performance Testing
The Dynatrace Server (backend process / service / daemon) is the core component of a Dynatrace environment and, in combination with the Client (UI), central configuration and administration unit.
It correlates PurePath data that it receives from the Agents via the Dynatrace Collectors and stores these (and also facultative thread and memory dumps,…) in the file system, the so-called session store.
It handles measures and their subscriptions.
The Frontend Server (frontend process / service / daemon) handles data analysis tasks (except big memory snapshots – see below) that Dynatrace Clients trigger.
As of Dynatrace 6 the Dynatrace Clients connect to the Frontend Server. (see schema above)
Currently the Frontend Server must be on the same machine as the Dynatrace Server.
The Memory Analysis Server process / service / daemon (formerly Analysis Server) is purely for post-processing memory snapshots to offload resource usage from the Dynatrace Server. With the same goal the new-to-6 Dynatrace Frontend Server serves all the other analysis data requested by the Dynatrace Clients.
The Memory Analysis Server may run on the same machine as the Dynatrace Server, if you have sufficient memory and processing resources. You may need a separate machine for huge memory snapshots or if the Memory Analysis Server is shared between Dynatrace Servers.
The Dynatrace Collector processes / services / daemons (up to dozens) – as the name implies – collect and bundle data from the Dynatrace Agents. (up to hundreds or more) Regarding network they must be relatively close to their Agents (same LAN), but can be far (Internet) from the Dynatrace Server.
Laid out redundantly they provide load balancing and fail-over. (Agents can fail-over to a different Collector.)
Collectors post-process the data to both, off-load from Agent and Server side and send the payload to the Dynatrace Server.
They also execute monitoring plugins that do not require an Agent.
The Dynatrace Performance Warehouse (SQL database server) stores processed measure / time-series data that the Agents deliver. Depending on the complexity and data volume this can be in a local database on the same machine or a high performance DB server.
As opposed to time-series data, PurePaths and thread and memory dump BLOBs are directly stored in the file system. (“session store”).
The Dynatrace Client (UI) is the presentation layer installed on users’ machines or started via a browser. (Webstart Client)
There is also a portable Client (for portable media like USB flash drives) that does not need installation (just unzip) and Dynatrace Web – the browser-based solution. (as opposed to the Webstart Client that is started via a browser and loaded from the Server).