Are there any compatibility issues or concerns for a SSD with a Dell D820 or D830? We're looking to replace a failing drive in a D830 with an SSD. Any SSD recommendations? Gotchas?
If you stick with brand-names SSDs (Intel, OCZ, Samsung, etc), I can safely say there will be no issues at all. The SSDs reports itself like a hard disk to the computer.
Your Dell D830 uses a 9.5mm SATA 2.5" hard drive caddy, and most 2.5" SSDs are of the same dimensions and specs.
If you got the money, and simply want the best, go for the Intel SSDs, especially the latest Intel X-25M G2 series. It's probably the best SSD money can buy now. For a more budget-aligned SSD, go for the OCZ Vertex or Summit series. My only advice to you (since this machine is a workstation class machine, and I am assuming you are using it for workstation purposes), is to avoid SSDs with the JMicron controller, for it had potential longevity and random write issues.
Also another tip : learn how to optimize your OS for SSDs. For example, since SSDs are so fast, but suffer from slow random read-writes, alot of SSD users including myself turn off Windows Indexing. Look at the growing tips base found on the OCZ forum.
D830 will be fine, D820 will not. If you check Crucial's site you will find they do not offer SSD for the D820, only the D830.
There is a reason for that! I only found out after a very frustrating couple of months with an OCZ Vertex 2 in the D820, where I eventually had to return to HD after a few weeks because of recurrent intermittent but disastrous disk corruption and BSOD's. The D820 has a kludged implementation of SATA which uses a bridge to PATA that has timing issues with SSD. There is also no AHCI. No fix is possible. D830 has none of these issues.