Both quad SSDs adapters had a fan on it and the built in M.2 ones had a heatsink, right in front of one large chassis fan & air intake. I didn't measure the SSD temperatures, but the I/O rate didn't drop over time. I was bottlenecked by CPU when doing small I/O tests, I monitored the current MHz from /proc/cpuinfo to make sure that the CPU speeds didn't drop lower than their nominal 3.9 GHz (and they didn't).

Btw, even the DIMMs have dedicated fans and enclosure (one per 4 DIMMs) on the P620.