The single most important component to insure good LR performance is the processor (CPU). Use the fastest (GHz) and most current quad-core processor you can afford (not six-core). Next in line is memory and 16GB should be the minimum. LR CC has also added GPU acceleration so follow the suggestions here: Adobe Photoshop Lightroom Help | Lightroom Graphics Processor Acceleration (GPU) Troubleshooting & FAQ
LR does not benefit much by using multiple drives. If you're building or buying a new system I would suggest configuring with a 256GB SSD as the main system drive for OS and applications and a 2TB or larger HDD for media files (Pictures, Videos, Music, Documents). You'll also need an external backup drive that is at least 2TB. The SSD will speed up OS boot time, application start up time, and LR to a lesser extent. I'm running LR CC with a 256GB SSD and 2TB HDD with numerous applications and ~28,000 image files and both drives have ~50% free space remaining. Once you hit ~15% free space it's time to move files to a 2nd drive or install a larger drive. A 256GB SSD should be fine for most photography users, but power users with lots of gaming and/or video editing applications may benefit from using multiple SSDs. The HDD should be chosen based upon the current "size on disk" of your media files (Pictures, Videos, Music, Documents). Multiply that by at least 2X to allow sufficient space for new files, but I would recommend 2TB as the minimum size. SSDs and HDDs are relatively inexpensive today so no reason to skimp. Here's what I'm using:
Thank you so much. Very good info.