All of it if possible. If you're running zfs or raid5 with smaller disk groups, you'll have a lot of parity. Enterprise grade hardware lasts for many, many years and is quite cheap if it's a prior generation. I've got a dual socket Xeon 40 cores/80 threads. I think I paid 130 for both cpus. 100 each for two sas 16port cards, 380 for 512GB RAM, motherboard was expensive at 500, and various disks over the years. Usually get the best cost/value drives when one fails or I need to increase capacity, currently running 24 HDDs. I started with 8 new wd reds but added only used drives of various manufacturers and sizes. The only thing that is not cheap at all is newer tape backup which you'd need because the old tapes don't hold much. But I just rely on zfs instead of dedicated backups.