After months of reliable use my Elgato Thunderbolt 2 hub is dropping my USB3 external SSD; just like the OWC T2 hub did in my initial testing.
We know Yosemite (and El Capitan) have issues with Thunderbolt hubs; there’s something frail in Apple’s infrastructure . But it had been working… So after power cycling everything  it’s time to look for things that have changed recently.
The first place to look is my Login items. I find something called “Mountain”. It’s missing though. Weird. Part of something I’d tried then removed. Deleted that.
I also find AOUMonitor. That would be related to my recent ScanSnap update. Sounds familiar, so I use my Google Custom Search for everything I’ve published. I find Managing unwanted Mac startup apps: ScanSnap’s AOUMonitor and Citrix Receiver. Bang. AOUMonitor is a known bad actor. Delete it.
Next is Google Drive. It’s known to cause problems, but I’m still hooked on it and it’s an old-timer. Despite Google’s decreasing interest in iOS and OS X  I have to leave it.
But where’s Amazon Cloud Drive? It’s a newbie that’s also launching automatically. The fact that it’s absent from Login Items tells me it’s poorly written. Over to LaunchDaemons.
System Library\LaunchDaemons looks all Apple — as it should be.
Users\Library\LaunchDaemons has CCC (ok), Office (licensing and update, ugh), Skype (huh? - deleted!), Google keystone (old, part of their update infrastructure I think), TripMode (? delete for now), Barebones (trustworthy).
Users\me\Library is a bit odd. Instead of LaunchDaemons we have LaunchAgents (really Apple?)  and no Startup Items. In LaunchAgents I find simple plists for Synology CloudStation (yeah, I’m suspicious of that one, but need it for now), 1Password (need it), Safari (ok I guess) and com.imobiesilentcleanserver.plist. The last was probably left over from testing imobie’s iOS cache cleaner (didn’t work), so I deleted it.
Alas, I still can’t figure out how Amazon Cloud Drive is starting up. Now I really want to kill it. Google is no help (which is another bad sign). Looking at Log files it looks like ACD is using some .NET infrastructure and it’s generated about 15 Console crash logs.
Amazon Cloud Drive is a bugger to purge. EasyFind finds a folder in .local/share — yeah, a hidden directory. There’s app.com.amazon.clouddrive.mac.installer.playlist in friggin’ /private/var/db/BootCaches/2B1FD298-BBE8-4207-B1B0-ED420A2DAD74. There’s crap in Application Scripts, Application Support, and too many to mention. Try searching on “Amazon Cloud Drive”, “amazon.clouddrive” and so on. Take your time.
Really, don’t touch Amazon Cloud Drive. Now I’m getting DOS TSR flashbacks in addition to my SCSI flashbacks.
Lastly, a safe boot to clear caches and then a restart. Now we’ll see what happens. I never did find what was launching Amazon Cloud Drive, but my Console isn’t showing any “Amazon” messages.
- fn -
 I’m getting PTSD flashbacks to MacOS Classic and SCSI chains.
 Apple is not doing well.
 I’m going to start routinely power cycling my peripherals — they can go weeks without cycling whereas my Air gets cycled every week or two.
 Update: jws explained - "The difference between an agent and a daemon is that an agent can display GUI if it wants to, while a daemon can't. The difference between an agent and a regular application is that an agent typically displays no GUI (or a very limited GUI)… Agents run in a user context; daemons are userless and purely background, without any access to a window server or other user state. That’s why the daemon vs agent distinction in the Library folder names…