I'm a total noob but I'm very interested in seeing how this turns out as I am a heavy Lightroom user and am currently trying to decide between FreeNAS and Synology. (My current rig is a Win7 machine with internal RAID5 that I have outgrown.)
My background is primarily networks so I have some questions/suggestions in case you haven't already tried them:
You mention you're using a Cisco switch. (What model?) Have you been able to rule out the network? Is it just your PC and the NAS on the same switch?
Regarding Lightroom, have you tried testing this with a new empty catalog, just to see if it has anything to do with it? Some of my catalogs are very large and I have noticed inconsistent performance problems, especially on imports. I know you said you did a parallel copy outside of Lightroom and it was slow as well, but I'm assuming you mean from the same PC. If at all possible, I would try the parallel copy from another PC while you're experiencing the slowness, just to rule out your Win7 PC and/or Lightroom. I would also try opening Resource Monitor on your Win7 PC to monitor network, disk and CPU activity while you're doing your imports. This is a great tool to help troubleshoot bottlenecks and may help you see what Lightroom is doing behind the scenes. One last comment about LR. There's an option that autowrites a metadata sidecar file (XMP?) for each of your photos, as well as the usual metadata in the catalog. I think those get written out to the same folder as the RAW files, which can result in random performance problems according to Adobe. Just a thought in case that's what you're doing.
FreeNAS vs. Synology: I had similar options and decided for FreeNAS because of ZFS support (my main priority is data integrity)
Router: Cisco/Linksys EA6300. PC and NAS on the same switch.
I'm now testing a direct connection PC-NAS. So far so good but being the issue intermittent I need more time to confirm that it's following the router.
Yes, the parallel copy I mentioned was from the same PC running Lightroom. I haven't been able to test copying from a second PC yet but I'm planning to do that.
The issue happens with catalogs different in size, creation date, etc. etc.
XMP sidecars are disabled.
I've been monitoring through Win7 Resource Monitor from the beginning: nothing to report, apart from the slow network speed
I'll keep posting if I'm able to make any progress.