It has 4 SATA SSD drives
120GB - for the system itself
2x 960GB
1x 480GB
And it has 4 NVMe m.2 drives
1x 4TB
1x 250Gb
1x 750gb
1x 960GB
They all run as a single btrfs drive mode with no redundancy.
Been like that for almost a year now so far and all the drives we're previously used in other systems that I have before I put them in the nas.
Absolutely zero issues. Love it. Every single time that I've tried using a rotating drive in an nas it just fails. Be it a WD red NAS drive or some random laptop HDD I have lying around.
Don't listen to people that say ssds fail.
The way prices are going right now I'm going to try to pick up more of the four terabyte nvme drives and replace the rest of the nvme drives in this nas one by one. If I could get every drive except for the small system drive to be a 4 TB drive that would rule.
But there is one exception. I have had reliability issues on this machine using a external nvme dock that's over USB c. And it's only with this particular OS or maybe it's just with Linux because it's fine in Windows and it has to do with how the dock doesn't give a unique serial number to the drive and also sometimes it just provides a very flaky connection and I was having a little bit of problems with that and as soon as I removed it from the array all the problems went away.
Honestly I'd love to have a sad based fast-Nas too, also attached. I was going to chime in to complain that there aren't good toaster carriers for nvme drives, but there actually are more than plenty of low price single drive USB carriers.
To me the question comes down to need. Mostly I need some good reliable bulk storage. I don't really need speed. It'd be fun to have a couple TB pool of fast storage, but not needed, where-as I need capacity badly. Getting some Seagate Exos spinning rust is just a no brainer, just fabulous drives at a great price.
SSDs can be faster but also less predictable and reliable. SSDs are more highly software oriented so they are more error/bug prone and performance can vary over time and based on usage and utilization patterns.
For example, it is not uncommon for an SSD at 75% of capacity to have significantly reduced read or write performance than it has at 25% of capacity.
This very forum has been affected by SSD bugs in the recent past.
The price difference was not that great so it was hard to justify buying slower spinning disks. We were looking at high speed spinning disks vs SSDs. If you are looking at slower speed drives maybe the math works out a little differently.
"Slower" is not always easy to judge. Lots of SSDs (if not most) tend to slow down as they start to fill up.
Use mirroring if losing everything on the drive would hurt.
Simple mirroring may not be enough.
SSDs have been known to fail based on power-on hours --- which means mirror and main die at roughly the same time.
This has affected HN in the recent past. https://news.ycombinator.com/item?id=32048148
IMO, SSD's became the standard a few years back.