As far as "support" goes, you'll be hard pressed to find this spelled out in the documentation. Most 10th-generation and newer Dell servers have good documentation available with a list of all of the supported drive models, but I've not seen this for the 2950. I can tell you from personal experience that the 2950 never introduced SSD support of any kind. With that being said, it may still work since communication is through a SATA interface. You run the exact same risk as with using any other non-Dell-certified drives, in that there may be problems with a specific model or drive FW that never gets addressed if it's non-certified (hardware and firmware validation testing are only carried out w/ Dell-branded drives). In the end, unless you can find an instance of someone having documented a test with the exact hardware combination as you (same server, controller, and SSD model), you're just not going to be able to know without testing it out.
In regards to comments on controller performance... The PERC controller itself can often become a bottleneck when using SSDs, especially when you get into older (ancient) cards like the PERC 5/i, and even newer cards if your I/O footprint is write heavy & random, e.g. a database of some kind. Go with the newest card your system is compatible with (PERC 6/i) if it's an option for you.
Another note on performance - LSI controllers (rebranded as PERC w/ Dell) don't currently support SSD TRIM like typical (newer) desktop integrated RAID controllers do. Long story short, that means that you're going to see very poor write performance after a bit of use unless you use a model w/ built-in garbage collection (e.g. SSDs with Sandforce controllers, like those made by Intel).
