The Synology Diskstation has been working very well for a few years now. I have already upgraded the disk space a couple of times and added more functionality.
But now the DS218j is becoming a little overworked.
I recently took the decision to upgrade to a more powerful model and, after a couple of weeks of investigation, chose the DS723+ device.
With an AMD Ryzen processor (2.6GHz) instead of the Armada 385 (1.3GHz), and 2GB RAM (upgradeable to 32GB) instead of the fixed 512MB, the specs seem much more impressive and capable.
I am running a file server, media server, photo server, various websites, and a MariaDB database server for the websites, the camera security system, and general playing around. All of this was keeping the older server running at an average of 15-40% processor use and over 70% memory. The new machine barely notices the load and CPU usage rarely goes over 20%, even after uploading new media files.
Upgrading the system was not too difficult. I opted not to attempt the migration assistant or the drive migration process, both of which seem too slow and potentially dangerous.
Instead, after backing up all of the relevant data to a separate hard drive, I simply deactivated the second drive of the RAID pair and removed that drive from the old system. The old server can now run happily as a single drive for the duration of the upgrade.
After installing the drive in the new server, setting up the base system, installing all the relevant software, and performing all the updates I had two servers running.
Next, I configured all of the server options and created the relevant websites, system shares, and other settings. The 'static' data such as music, photos, and videos was copied to the respective folders on the new server, a fairly slow process done with 'rsync' and write validation.
One by one, I copied the data from each website and enabled it on the new server, finally I changed the port forwarding on the internet router to direct access to the new server.
The final item to migrate was the Zoneminder surveillance system database. I stopped the service running on the Raspberry Pi, migrated the MariaDB database to the new server, changed the Zonemider config to use storage on the new server, and restarted the Raspberry Pi. Everything worked fine.
With all the data safely copied to the new machine I renamed the old system and closed it down. Then I changed the name of the new system to that of the old system which means that all other systems accessing the server do not need to change.
The new system was left to run for a day while I ran tests and checked the logs for problems. Once I was satisfied all was good it was a simple matter to remove the second hard drive from the old system and install it in the new machine. The two drives were configured as a Hybrid RAID (basically a data mirroring process) to ensure data integrity in the case of a disk failure.
The only significant change I made to the new system was to format the drives as btrfs file system instead of ext4 format. This does not seem to have affected the performance of the disk access and it seems to work very well.
This system should now be useable for many years. Upgrading the disk space can be done very easily, though the current 4TB is only half used at this time. Also, it is possible to upgrade the RAM to 32GB if and when I decide that it is necessary.