Have an R720 also with the H710 flashed to IT mode running TrueNAS Core as my primary on-site storage system for about two years now with absolutely zero issues. It is essentially a stock R720 with the OEM HDD cables and other internals. For context, I am an IT service provider like Tom, so my systems are running in production daily doing real world stuff. My stack is lots of VMs running on 2 other dedicated XCP-ng servers (main XCP-ng is an R720 and the other is old R710 that gets powered up for some one-off stuff as needed).
The core systems of the business are all VMs and the lab system is used for building proof of concept systems and projects for clients. Lots of large datasets with the VMs and then the typical small document and typical file type data. Almost every system in production and lab systems point back to the TrueNAS core R720 for storage with SMB, NFS and iSCSI. Can tell you there are no issues with any of my R720s, and they both preform well.
Suggest not over thinking the R720. I vote for the R720 and recommend you look into used SAS HDDs Got (12) 4TB HGST for $500 shipped. My TrueNAS R720 has 8 HDDs and 4 spares for cheap. The SAS drives can be cheaper than the SATA drives because consumer and most homelabs can’t use SAS. Got my R720 for $300 with 192GB of RAM, $25 for a SATA DOM and a SolarFlare 10Gb NIC for $50 so the total for my build was $875 then $50 for an iDRAC 7 Enterprise License, so $925 with all the bells and whistles with 4 spare enterprise grade, heavy duty, high performance 7200 RPM SAS HDDs.
The TrueNAS is configured RAID Z2 with 20TB of storage. Right now the system is loaded down heavy with data pulled in from all my personal and other old storage systems that is being organized and cleaned up. Also lots of VMs and snapshots related to my new Invoice Ninja v5 server. Have 2 test VM instances and additional one that is the production build with a slew of snapshots and forks testing different iterations and configurations.
