I have a 256SSd connected via a SATA to usb wire connected to the shield and using it as device storage as my shield only has 16gb or internal storage. The only difference is that I have a ds1618+ which doesnt have hardware transcoding so I have to use the shield as the sever. I an usind the exact comfiguration you are asking about. You can activate HDD hibernation on the nas, when the shield tries to access data from the nas, it will wake up. Yes, the shield will keep the ples server even if the shield itseld is asleep. Even if you restart the shield it will reconnect to the nas so no worries on that part. Yes, you can mount you nas on the shield and you can run the pex server on the shield and point the location to the nas. Also if the ssd or flash drive dies then you are in trouble. You can use a flash drive or a ssd as device storage and keep it connected to shield but there is sometimes an error where plex cant find the ssd and it tells you to set a new plex server. Shield doesnt have a ton of space unless yo uhave the 2015 model shield. Plex metadata takes up a lot of space especially if you use the chapter preview with I personally love. Ds918+ has hardware transcoding same as the shield. I would recommend sticking with the ds918+ especially if your media is stored on the NAS itself.

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