Power supply and case I’ve always bought new. Everything else has been 100% used enterprise parts off eBay, or used hand-me-downs from my gaming rig. No issues in 15 years doing this.

My NAS is almost filled with used parts, mostly lightly used. Only the power supply is brand new as the form factor is hard to find.(flex ATX, I bought an FSP FlexGURU)

IMO excluding HDD, most hardwares can be used without much consequence: CPU, RAM(I only trust original/major grade sticks), case and perhaps power supply(from reputable brand and known good model)

Aside from drives, the rest of the components are fine. But honestly, I use what I had for a computer before upgrading to my current one. Old components you have around can be a good idea.

I don’t really like buying drives second-hand, but I suppose it shouldn’t be an issue if the drive is relatively new and has had little use.

Motherboard, CPU and RAM - no problem at all (more accurately, problems are easy to spot with diagnostics and they shouldn’t wear out).

Chassis - a bit of a wild card. The backplane in one of my systems is faulty.

PSUs - ideally new.

HDDs - almost all of mine are secondhand. Enterprise- or NAS-grade drives should have many years of life left. Ideally buy new to benefit from warranty but my experience has been great.

SSDs - nope. Buy new. I bought some secondhand Samsung SSDs and they developed problems, both threw IO errors after a few weeks. SSDs are cheap enough not to bother with secondhand.

Everything else I bought used, including the rack. In fact, the only things I bought new in my entire homelab are my router and WiFi AP.

The only thing I buy new are the HDD’s for the bulk storage.

I’ll buy used enterprise SSD’s for flash storage.

I have purchased entire used machines before.

My current setup is all used, except the mobo cause mini ITX LGA 1200 is a pain, and the PSU cause I got a great deal on that passive one. But they could also have been used.

I’ve purchased almost everything used except for the case (using a Fractal Design Define 7 XL and Fractal Design R5).

Used/retired enterprise hardware has virtually zero market, so it’s dirt cheap.

I’m using Dell Precision motherboards and Intel Xeon CPUs in both of my main production servers because each motherboard/CPU combo ran about $30 each.

For hard drives specifically I almost always buy used, but I always buy enterprise/NAS drives (HGST DC, Seagate Exos, and Western Digital Red Plus to name a few).

My whole setup is used,

Paid 40 euro for a optiplex with 32gb ram and chucked in a 10tb HDD and a 2tb nvme Paid 55 euro for a Nuc with 24gb ram and it has a 500gb SSD and a 2tb nvme Paid 80 euro for a 730xd without disk’s ram and CPUs

Paid 19 euro for two 2630Ls Paid 35 euro for 26 2’5 caddies Paid 11 euro per used 1tb micron ssds (got 24 of them ) Paid 140 euro for 256gb ram lol

Ive had good luck with used enterprise hdds. They are loud but have always worked fine. I like buying them all at once from the same seller, but I’ve mixed and matched as well.

I personally don’t think smart errors are the end of the world either. A few of them on something large like 14tb isn’t the end of the world. I’ve had more issues with brand new seagate 8tb than anything I’ve gotten used.

Everything used. Any risk of drive failure can be offset by just buying more drives.

For me, everything is on the table for used with a minor exception for spinning drives which I tend to buy new. There are some good recycling companies out that that have killer deals on enterprise setups. A lot of those also have enterprise activated idracs (dell hardware anyway)for example which saves me time running up and down stairs trying to get it setup or investigate why I can’t ssh into it.

For example, I picked up a dell 720xd from a recycling company for $450 shipped - 256gb ram, 20 cores(40threads), enterprise idracs, 12x4tb sas, and 2x 300gb ssd for os. Is it louder than a setup I could build, absolutely. But I needed something to replace my Amazon drive for my photos and this was way cheaper than adding 10 more drives to my main nas setup(I would have done >14tb drives in there)

I get used everything. Even drives. Where you buy it and how used it is matters.

I’d probably buy everything used other than the power supply and drives.

My entire NAS is used parts, including used enterprise HDD’s. I put the gear through a thermal, memory, and IO stress tests and all checked out. I bought 10 drives when I only needed 8 with assumption that at least 2 would be bad (none of them were and they’ve been in use for > 2 years). Correction - the case was new, I uses a Rosswill rackmount.