Hello I have 2x TL-R2400PES-RP-US enclosures, and I wanted to know if it is a support and recommended practice to span a storage volume across both enclosures. I know Synology does not recommend this, but I want to know what is QNAP’s take on this. I have a TDS-H2489FUR2 head unit that will only have a storage volume within its own chassis, but I want to know if I can span the storage volume across the enclosures safely.
You cannot, and it would be very unwise. If the connection to one of the enclosures goes down, more disks are disconnect simultaneously and it it bye bye raid.
@Jamal I’m curious what you ended up doing here, as I’m in a very similar situation. Also, are you running QuTS Hero on the head unit?
I’ve spent countless hours reading and re-reading the support pages, QuTS docs, forums, GUI tooltips, product descriptions, compatibility lists… And I still can’t find a 100% reliable answer as to whether or not this is possible. Whether or not it’s recommended is a different discussion 
I can tell everyone from experience (learned the hard way) that you definitely cannot use one of the cheaper SATA JBOD enclosures like the TL-R1200S-RP to expand a storage pool existing on the host NAS or another enclosure. When you go to Expand Pool > [Add new disk(s) or RAID group] > Select Disks, only the pool’s current location (NAS or expansion unit) is selectable – Everything else is grayed out and says “Not supported currently” when you hover over it.
I’ve found official and unofficial sources that say this configuration is possible but only with the right combination of host NAS and expansion unit. I’m hoping that is the case with a TS-h2477AXU-RP NAS + QXP-3X8PES card + TL-R2400PES-RP expansion.
For my use I absolutely need a single, large, expandable storage pool – This seems like it should be a common use case. Actually, to be more specific and use QNAP terminology, I need a single Shared Folder (aka Thin Volume) that I can continuously expand by adding additional 4-wide RAID5 groups to the master RAID50 Storage Pool as needed. I don’t even care if it technically spans across multiple independent Storage Pools (one per enclosure) in the background, just so long as it presents to SMB clients as a single unified Shared Folder.
Side note: I previously had the two R1200S enclosures connected to a custom PC running TrueNAS, configured as described above (single pool made up of multiple 4-wide vdevs across multiple devices). Initial setup was easy, as was expanding it when needed, and I don’t recall having any issues over a year+ of daily use.
