Which brand of disk do you recommend?

I've had good experience with Seagate EXOS drives so far in my primary NAS (12 of them).

I also have for a longer time a dozen Ironwolf Pro's in my secondary NAS, but I've replaced 4 of them over the years due to them developing bad sectors.

Anyway: I'd always pick enterprise grade over NAS grade nowadays.

Do read the spec sheets e.g. an EXOS like above mentioned has twice the MTBF (mean time between failures) rating of an Ironwolf Pro.

But I'd start with the infamous "compatibility" list for your model NAS. If you can picking from that list makes it a more likely to get support to want to look at your problem (they're a bit famous for not wanting to look at any problem if you have any hardware not in that list).

/r/synology Thread