The main idea behind the storage in a NAS like Qnap is to use multiple disks (preferably with some disk redundancy) put together in larger volumes. Not as a connector of many stand-alone disks.
Peter.Hahn wrote:1) Can I connect external USB and eSATA drives to the NAS and share their content on the network?
Yes you can but external disks are primarily meant to be used as backup destinations, not as shared resources so there will be severe limitations.
User access rights aren't supported down on folder level as they are with internal disks. Also upon reboot multiple disks may change share names making it very complicated to manage with anything but very educated users. There may be even more complications I'm not aware of.
2) How many external drives can I connect to the TS-419P II via USB (via a HUB?) and / or eSATA?
USB-hubs may work (the thought to try never even crossed my mind) but I would be extremely surprised if there was any support for it. Generally I find hubs a bad idea with storage devices.
I think the number of external disks supported is the same as the number of available physical ports (so of course less if any other USB-connected devices are also used).
This is the list of supported external disks. Many other does work as well but there are no guarantees.
3) Can I connect USB and eSATA drives at the same time to share their content on the LAN?
Yes. In fact one of each would be my recommendation if you intend to use them as shared disks, to avoid the previously mentioned problem where multiple external disks of the same type (USB or eSATA) may change share names.
4) Can I connect USB dirves and USB printers at the same time (via HUB)? Does this have influence on the number of drives / printers?
Up to 3 USB printers are supported. See answer above about the number of disks and when both types are used.
This is the Qnap list of supported printers.
5) How will I get updates for the Twonky Media server? From Element5, from QNAP, from the community?
From Qnap. Historically not every Twonky-release have been brought forward by Qnap.
No, RAID has never ever been a replacement for backups. Without backups you will eventually lose data!
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TS-559 Pro II 3*HUA723030ALA640 RAID 5 | TS-459 Pro II 4*HDS722020ALA330 RAID 6 | TS-419P II 2*WD30EFRX RAID 1 | TS-119 ST3750640AS | TS-219P HDS722020ALA330 | All with APC Back-UPS ES BE700G-GR