I used 2x Seagate Ironwolf 510's for first
720+ as they WERE LISTED in Synology's Acceptable Hardware List.... And worked fine!
When it came time for second 720+, The Seagate Ironwolf 510's were still on the list, as were but not available-anywhere, Seagate came out with a newer model.... That Model was NOT ON LIST!
So I contacted support.... Asking when new Seagate will be put on list? Support read off a flip card threatening not to support me, etc, etc..... and suggested that if Synology M2's were un-availble, refer again to the list so that I'd not lose my Warranty! So I looked for Samsung Enterprise M.2s.... These were not available either!!! Nor Samsung Mid-range models...
I did find 2x CONSUMER SAMSUNG M.2 that was in list, available, and works, but..... I would have MUCH RATHER WANTED TO USE THE newer SEAGATE Ironwolf !!!
That conversation with Support stuck in my craw and aggravates me-to this day!! Being a retired Component Level Engineer from a TV Netwrok, This approach did not make much sense... components are components.... Afterward, after reading multiple posts here and elsewhere that people were using other 3rd party drives (And I was already using 12-15 year old Barracuda's that were flagged as: "Not in Acceptable Hardware List" in that experimental 720+, as I didn't have $$ for new drives, and these were 'on the shelf' retired from use as Raid 0 array in video editing system for many years!!!) I thought: I KNOW THESE DRIVES ARE GOOD!!!! What the Hell, it's an "Experimental NAS" Let's Experiment!!!! Aftere first nag, nothing since!
So I've tried the following:
3rd Party RAM -- Has Never Prompted as un-acceptable!
3rd Party SATA Drives -- HDD & SSD -- Has Never Prompted as un-acceptable -- after first NAG... Quiet since!
3rd Party eSATA Enclosures --- With 3rd Party SSD inside -- Has Never Prompted as un-acceptable! Never even saw first NAG, like internal drives will!
3rd Party Power Supply --- No issuses whatsoever, and Synology Power Supply is now a spare on the shelf for any of the 3 NAS's we have
By the way, I recently looked at the 'list' and all 3rd party M.2's have been REMOVED! ONLY Synology M.2 remain on the list.... !!!
When the 3rd Party eSATA Enclosure with SSD Worked fine on "experimental" NAS, for 6 months.... They were added to my other two NAS's:
718+ & first 720+.... All 3 with 512MB-2TB SSD's are flawless in operation, and provide inexpensive redundant storage of important files!
I looked into the script file for using M.2's as storage, but seeing that my M2's are not that large, compared to external eSATA, they are better off used as Cache's, though I'm not even certain that as R/W cache's they are speeding things up significantly!