I am running Home Assistant on a PI4 with 4gb ram using externally attached SSD. It can show some lag at times. The PI is directly connected to the router. I have a Synology DS413 being surplus to requirements at present having done a recent NAS upgrade and was wondering if I would be better off running HA off the spare NAS. Thoughts would be appreciated.
Would need more detail on your statement ‘some lag at times’. That said, it has been a while but when I tried to do some SSD setups with rpi, due to driver issues I saw OS freezes due to IO being locked up to the SSD. I would think they have that sorted out by now, but I would review the various SSD configurations.Unfortunately, it seems there are many versions floating around. You could try just running off a SD card for a while and see if problem goes away.
All that said, because a rpi 4 with 4 gb ram is a much more capable machine that a 1 gb celeron DS413.
Good hunting!