I'm rather rusty and there are a few things in your syslog I haven't seen before, and I don't know anything about your previous network issues, so my comments may or may not be helpful. The "link up" messages are not errors, just an indication of a connection (or reconnection) to the physical network. There are a batch of these messages late in your syslog that do seem odd, in that they have no corresponding "link down" message, but I don't know the significance. They seem harmless, but the network driver may be a bit confused.
That is just the manual command to the Cache drive to spin down. It is not an array drive, so spin down is handled differently. Completely normal.
Hello.
Just my 2p and may not be any use. What type of switch do you have that your are plugged in to?
I have seen messages like that on other systems when the network port is flapping, ie coming up and down. Sometimes this is due to a speed and duplex issues between the device and the switch.
Just a thought.