10GBASE-T is pretty well established for top-of-rack datacenter switches. Intel's X520 chipset is pretty common and any major switch vendor will happily sell yo

10GBASE-T is pretty well established for top-of-rack datacenter switches. Intel's X520 chipset is pretty common and any major switch vendor will happily sell you a 24x or 48x 10-gig switch (HP's JG336A for example). Twinax is arguably better if you're building a rack from scratch, they're lower power, but if you're upgrading something existing it's hard to justify rewiring everything. Also twinax cables are expensive and annoying to work with.