Disk upgrade options for Precision 3660?

1.  Specification limit is the maximum capacity Dell tested and validated to use on the system at the time the spec-sheet was written.  They are limited to products available in-house and factory floor.  Dell does not want to extend support to third party products or maximum capacity available in the market.  With that said, you can add higher capacity to your system storage, although it won't be supported with the system warranty.

2.  M.2 RAID will be on different controller and may not be extended to SATA volume as planned.  Hardware wise, watch out for flexbay backplane and brackets may not provided with no SATA configurations. 

3.  To use two NVMe SSD on the adapter, the installed PCIe slot must support bifurcation which only available on 5000 and 7000 series.

Oh, yecch. I hadn’t thought about #2: On the 5810 all the disks are SATA so of course it can have two RAID arrays.

It looks like I’m going to have to go with the 5000 series.

Just want to offer a few key information.  There are different front flexbay options for the 5820, total of 4 drives can be used in the flexbay.  You can choose a standard backplane with all 4 SATA drives, or optional backplane with NVMe/U.2 on top 2 and SATA on bottom 2, or a specific backplane that can accommodate a dedicated SAS controller card.

Remember to select a system with Xeon CPU, that will allow access to more PCIe lanes than of a Core-X CPU.

For SATA RAID, one can utilize the 5.25" bay to add 4 more drives such as Icy Dock hot swap cage.

For NVMe/U.2 RAID, there are three VMD controllers which manage PCIe0/PCIe1 headers, Slot 2, and Slot 4.  After market VROC adapter can be used if having trouble sourcing Dell Ultra-Speed Quad/Duo.

If planning to use tri-mode MegaRaid controller, must select the chassis of 7920 to gain access of multi-flexbay.

I tried pricing out a 5820 and it is a lot more than even a minimally configured 3660. Part of it is that at least as measured by cpubenchmark.net, the i9-13000K available for the 3660 is much faster than most of the Xeon processors available in the 5820--and I'm particularly interested in parallel speed in which different cores have different workloads.

Typical use is in music production, where each track has its own core or cores and different tracks have (sometimes substantially) different cpu requirements.

Of course it's hard to figure out how different processors will perform under these circumstances.

What I realized is that I don't really need RAID on everything. I think it's worthwhile for the boot drive, because then if a drive fails, I can just replace it and rebuild the array, and not have to worry about things like software detecting a different boot drive serial number and cancelling its license until I negotiate with the manufacturer.

But for other drives, it seems that I would be just as well using the "storage pool" facility built into Windows 11, which appears to be what is essentiallly software RAID; these processors are so fast that I don't think I need to worry about performance loss on SATA drives.

FWIW, I wound up ordering a 3660. I asked the sales rep whether it would be possible to run two RAID arrays at the same time, one on the NVME SSD pair and one on the SATA pair. They checked with their technical support people and confirmed, in writing, that that was the case. I am skeptical, but the price difference between the 3660 and the 5000-series for comparable performance is just too great to disregard.

Also... SATA is limited to 6 Gb/sec transfer rate. USB 3.2 is either 5, 10, or 20 Gb/sec, depending on the generation. Therefore, it seems to me that an external USB 3.2 SSD should be able to run faster than ANY kind of SATA drive, RAID or not. Am I missing something here?

Tech support is correct, it's possible to have two separate RAID arrays in your system.  You just can not have RAID volumes spanning across controllers as the 7000 series.

As for data transfer rate, there is no point in comparison the theoretical specs.  Only when factoring in all the components capabilities, devices setup, and volume of workflow, the sustained speed is what you want to achieve. 

Still glad that you made the decision, enjoy your new workstation.

Ah, maybe I misunderstood you earlier when you said "M.2 RAID will be on different controller and may not be extended to SATA volume as planned."

I have ordered the machine shipped with two NVMe cards in a RAID-1 configuration and two empty SATA slots. I would like to put a disk in each SATA slot and run them as a second RAID-1 array, independently from the NVMe RAID-1 array. 

I haven't figured out what kind of disks to use yet. I'm going to start with two 6TB Western Digital Black drives salvaged from the old machine and do some benchmarking while I decide.

I had thought of maybe using a pair of 20TB Ultrastar drives, which are available at a very attractive price at the moment, but several independent reviewers have described them as obnoxiously loud. Also, despite Dell saying that the 3660 "requires" enterprise-class drives if they're bigger than 4TB, they also say that if you install any enterprise-class drives, that will prevent the machine from ever going into "modern sleep" mode.

I don't know how much of a problem this is. However, another possibility might be the recently released 8TB Samsung 870 QVO SSD. The low acoustic noise level might be worth it, and I think they'll be big enough for the next few years while I decide what to do next.

Anyway, it sounds like you are saying there should be no problem running two raid arrays at the same time, so long as one of them comprises the two M.2 slots and the other comprises the two SATA slots.