XPS 8950 -- How to configure RAID for two NVMe SSD drives?

This is what I understand of Dell RAID.

the two identical capacity hdd are now set up in RAID 0 which does not provide redundancy back up (like RAID 1) but runs in stripping mode for faster access.  It makes access to hdd a bit faster.

the single ssd selected serves as intel rapid storage cache drive for the hdd.  That is why you do not need a second ssd for this purpose.

you really do not need to (and probably cannot) set up two ssd of identical capacity in RAID 0 or 1 as that concept is for mechanical hdd. Your ssd is so fast already that applying stripping mode makes little sense.  SSD is not meant for data archive back up.  For long term security of data use hdd or external hdd for back up.

reference:

RAID 0 striped Disk Array with no Fault Tolerance - Provides data striping - spreading out blocks of each file across multiple disks, but no redundancy. This improves performance but puts all data at risk in the event of a disk failure. The drawback to this method is if one drive fails, then all data in the array - both disks are lost. The only benefit to this method is it speeds up write times to the drive which makes your computer quicker and it keeps the full size of the disks.

RAID 1  Mirrored Disk Array - Provides redundancy in case one of the two drives fails. This allows for all data to be duplicated, but is not as fast as a RAID 0. If a disk fails, the data can be recovered from the second disk. The drawback is you half the size of your total capacity, and it is slower to write and it does it to both drives. The benefit is if one disk fails you still have all your data and can rebuild from the surviving disk.

Thanks ... 
I understand what you say but the SSD (Controller 2, Port 0) is the Boot drive with the Operating System (C:). It's not a cache for the HDD. I added a second SSD (and a second HDD). 

I would like to setup the SSD with the Operating System in RAID 1 (= mirror) so that if it fails (which it will eventually) I can simply replace it with a new SSD. And the system "recovers" itself with minimal efforts. 

Pictures are not visible to me so I can't see the error/issue.  You could set up array for your NVME drives using Intel VMD or VROC.  Did you purchase a VROC key?  You can also use HighPoint RAID controller depending on your need.

Re: the SSD is the Boot drive with the Operating System (C:). It's not a cache for the HDD

Dell has been doing this Intel rapid storage config associated w RAID for a long time. Dell did this first in XPS 8500 then 8700 where they used a tiny 32 GB mSATA ssd as boot drive set up in RAID config w hdd.

My understanding is once it is set up this way, Windows does not see the ssd and hdd as two distinctly separate drives like you are used to thinking.  rather whenever a file is accessed, it is simultaneously performed both on the ssd and hdd to speed things up.

Smart Response Technology (SRT, also called SSD Caching) is a proprietary caching mechanism introduced in 2011 by Intel which allows a SATA solid-state drive (SSD) to function as cache for a (conventional magnetic) hard disk drive (HDD).  SRT is managed by Intel Rapid Storage Technology.

Intel® Smart Response Technology is a feature of Intel Rapid Storage Technology that recognizes and automatically stores your most frequently used applications and data into a high performance SSD while giving you full access to the large storage capacity of a hard disk drive (HDD). This enables a small-capacity SSD to be used in conjunction with a high-capacity HDD.

When it comes to your specific PC config, if you set up one of the ssd in the "Intel Optane and Storage management" (last screenshot you uploaded), I believe that ssd becomes the cache drive of Intel SRT.

Re: I would like to setup the SSD with the Operating System in RAID 1 (= mirror) so that if it fails (which it will eventually) I can simply replace it with a new SSD. And the system "recovers" itself with minimal efforts. 

I am not sure that would work but others may have better idea.

to recover your OS in case one day the ssd fails, simply clone it to a spare sata ssd and save the clone in your drawer.

@RJD54  - Why not make your life easy and simple...?

Just image your boot SSD on a routine basis and save the image on either your internal HDD or the other internal SSD, space permitting, or on external USB drive. That way, if the boot SSD fails, you can easily move the latest image back onto a new boot SSD.

You can use any imaging software you like, but Macrium Reflect (free) is a good choice. And you can configure Macrium to make images on a schedule. Be sure to select Macrium's option to validate the image immediately after creation, and also use Macrium to create a bootable USB stick that's you'd use  to restore an image from another drive, if the need comes up...

Thanks for all suggestions! And for the reference to the Macrium Reflect software.

If I can't get the RAID to work with the SSDs I'll try it. I'm using an old version of True Image (from Acronis) for an older setup but would love to try something different. 

To make "life easy and simple" would be to setup the SSDs in RAID 1. (I'll probably post the same question to Dell Tech. Support; it may not be possibly unless the BIOS is updated if the motherboard allows such a configuration ...)

Have you read Configuration and Setting up of SSD RAID 1?

No ... but I just did. It does not help. The "Storage Spaces" is a Windows application (under the Control Panel). Started it and it only shows the non-system SSD drive. Besides I prefer to stay with Intel apps since those I believe are working with the hardware in a different manner. 

BTW. I noticed that the two SSDs are listed on two different controllers (number 2 and number 4). I have no control of that. I don't know if that's the reason it won't work. But this is low level stuff and I believe now that it won't work unless it is supported in the BIOS. I have contacted Dell Tech. Support. I will post here once I have an answer (one way or another).

Thanks!

If I am looking at your photos correctly, you have Optane Memory enabled on port 2. I read somewhere that before you can enable both Pcie SSD's as a Raid Array you have to turn of Optane Memory. 

Here's a photo of mine. You have to reboot after turning off Optane memory. Hope this helps. 

I should say that the Dell OS Recovery Tool (latest version) has a copy option to clone the system drive. I used it to clone the 512 SSD that came with the system to a Samsung 1TB 980 Pro SSD drive (it extended the "user" partition automatically; the macrium program can also be used for this purpose but one has to pay attention to partition sizes ...). The tool is here:
https://www.dell.com/support/home/en-us/drivers/osiso/recoverytool

Hope this helps.

Thanks to everyone who has responded. I should have posted my findings earlier. The short answer is that the XPS 8950 system allows RAID system configurations (RAID 0 and 1 using built-in slots for PCIe and SATA drives) BUT please notice size of drives required discussed below. (BTW system works fine with 3 SATA drives as well and 2 SSD drives for a total of 5 drives.) Also I should say that my system does not have Optane Memory so any references (discussions) thereto are not applicable.

I have been in communication with Intel and I'm doing a copy and paste here:
---
I completed the testing. I confirmed that the second drive (non system drive) has to have a bigger size. Otherwise it won't let me create a RAID System. I did two tests.

1. System drive 512 GB and second drive 2 TB (these are the official sizes not sizes available for user data)
Worked. I also completed the RAID1. See screenshot with Volume size 477 GB. Didn't know how to delete the RAID. VERY POOR documentation. In fact, there is none so if you can provide documentation on how to the delete the RAID would be appreciated. The drives I played with were copies so I could afford to mess up. Which I did ... I changed the type from RAID 1 to RAID 0. Didn't help. No easy way do delete the RAID 0. I suppose that would be more difficult if one wanted to save the data. I noticed that for RAID 0 the size was in the upper 900 GB range (and not size of drive 1 plus drive 2). Strange. I didn't save a screen shot.

I finally figured out how to delete the RAID 0. I was able to use the Intel Optane Memory and Storage Management program with the 2 TB drive attached to the motherboard but booting from another drive. Then I was able to delete the 2 TB drive RAID setup. Very confusing. There is no CTRL-I to enter a configuration management at boot time. Tried many different ways. As I recall with only one of the 2 RAID 0 drives installed it wouldn't boot. Further cause for confusion is that the system would boot from either of the two SSD slots on the motherboard.

Finally I was happy I was able to delete the RAID and decided not to mess around with it. I'm not going to use RAID 1 either. Instead I have decided to make image copies of the system drive regularly with the program called Macrium Reflect.

2. Two 1 TB Samsung drives
Would work for both RAID 1 (932 GB; see screen shot) and RAID 0 (about 2 TB; did not save screen shot). I did not proceed with creating any RAID system.

Bottomline is that the system provides capability to create a RAID system. But the second drive needs to be bigger than the first (or same size) for RAID 1. Documentation is very poor! (In my case system drive was 512 GB and second drive was 500 GB; didn't pay close enough attention).

Thanks

A few final notes and then this thread can be considered solved. For the second drive bay there is no drive caddy provided by Dell. Nor can you buy it from them. I got one from Amazon and one from eBay. Both work. Here are the links.
https://www.ebay.com/itm/174252673421

https://www.amazon.com/dp/B08PK47Y7H?psc=1&ref=ppx_yo2_dt_b_product_details

You would also need a SATA cable (left angle; 18 inch long enough).

https://www.amazon.com/dp/B000FHGW5K?psc=1&ref=ppx_yo2_dt_b_product_details

Thanks

Pics of referenced caddy's and SATA cable.