XPS 8950, installing two additional HDD

@HP9000258 There are instructions in the Service Manual: https://dl.dell.com/content/manual30492141-xps-8950-service-manual.pdf?language=en-us&ps=true

You will need a SATA data cable for each of your drives. For the 2.5" drive you will need a 2.5" to 3.5" mounting adapter. Also, you will need two hard drive carriers which you can purchase from Dell since I do not believe they are included inside your PC. Open your PC and have a look around. 

Re: 

• Does the 8950's power supply cover those extra hard drives?   Yes
• If it does, what would I need in order to install them?  See 1st reply
• The evo drive has an OS installed on it from the previous PC, does that need to be considered before installing?  If previous OS was installed via UEFI, should be plug n play.  If legacy bios, need to convert from MBR to GPT.
• Is there anything I haven't mentioned that I'd need to consider?  maybe a good idea to back up data and do a clean Win 10/11 install than moving old OS from old pc because previous install may have accumulated ponderous inefficient files and potential malware.

Specs for this PC say:
Up to two 3.5-inch hard drives + up to two M.2 2230/2280 solid-state drives

So if you don't have any HDDs installed now, you could install both of your existing HDDs, but the 2.5" SATA SSD is going to need some sort of adapter tray to fit in the 3.5" HDD carrier, or an adapter that can be used without that HDD carrier. Service Manual has instructions to install HDDs.

The image in the Service Manual looks like there's one SATA power cable with connectors for two HDDs on the same cable.

You're probably going to need to get two SATA data cables, which are readily available on line. The image in the SM shows a 90º connector on the data cable, at least on the HDD end, so you'll probably want to get the same type.

Windows on the NVME SSD is probably installed with BIOS set to RAID, so you probably want to change that to AHCI before installing any new drives. This has to be done the right way or you'll make the PC unbootable:

1. Open Cmd prompt window, Run as administrator
2. Copy-paste this command, which will start Windows in Safe Mode the next time you boot: bcdedit /set {current} safeboot minimal and press Enter
3. Restart the computer and enter BIOS setup
4. Change SATA Operation mode from RAID to AHCI
5. Save the change and exit Setup and Windows will automatically boot in Safe Mode
6. Open Cmd again, as in step #1.
7. Copy-paste this command, which will start Windows in Normal Mode the next time you reboot: bcdedit /deletevalue {current} safeboot and press Enter
8. Reboot and Windows will automatically start with AHCI drivers enabled

NOTE: It would be a good idea to image the NVME SSD using something like Macrium Reflect (free) and save the image on an external USB drive, before you follow the above steps to configure the PC to use AHCI, just as a safety precaution.

As for the 2.5" HDD with the OS on it, Windows Boot Manager may try to boot from it every time you power on. But since it's from another PC, the OS may not be configured correctly to boot this new XPS 8950,.

The best thing would be to image this HDD while still in the old PC using Macrium, in case you ever need to boot that PC again. Then install the HDD in the XPS 8950, assuming you have a suitable adapter to mount it in the 3.5" HDD carrier and data cable.

You'll have to use the F12 boot menu option to boot directly from your NVME drive, as long as that HDD has the OS on it. After you boot from the SSD via F12, use Windows Disk Management to initialize the HDD (ALL FILES DELETED!). Once that's done, you should be able to boot normally, directly from the NVME SSD, and the HDD can now be used for routine storage or backup.

I'd install one new drive at a time, and make sure the first HDD works properly before adding the second one...

Thanks for the super quick replies!

I think I have a better idea of what I need now:

2x SATA data cables

• Is it just one that needs a 90º connector (for the 3.5" drive)?
• Will the 8950 have the power cables for the extra 2 drives?

Mounting adapter for the 2.5 SSD

• Is this the one I'll need? - https://www.dell.com/en-uk/shop/dell-2x-25in-hdd-caddy-for-xps-8950/apd/575-bcme/storage-drives-media#tabs_section
• For the 3.5" drive I'm guessing I need to check if one of those blue things it should sit in is inside already

redxps630 / RoHe - as far as the OS being on the SSD goes, I'm not looking to replace the existing OS with it, I plan on sticking with Win11 on the preinstalled m.2 drive. I just want to be able to access it and wipe it for it's space, to use as a separate hard drive for games. If I got ahold of everything I needed, hooked it all up, and started the pc, would the OS being on there cause problems?

I had it in my head that I'd install the 2 drives, boot windows up, use the HDD as I'd done on the previous PC, for storing files, and clear everthing on the SSD.

You probably will need a 90º connector on both SATA data cables. 

The XPS 8950 PSU likely comes with a permanently attached SATA power cable. Based on image #4 here it looks like there are 2 SATA power connectors on the same cable. So assuming both drives go into the same space, that should be sufficient.

The caddies you linked seem right for a 2.5" drive. It appears to be a pair of them. So the only other question would be is if you can mix a 2.5" drive and a 3.5" drive, each in the right size caddy, in that space.

You still should reconfigure Windows 11 and change BIOS from RAID to AHCI before installing any new drives, as I mentioned above. Otherwise, you may get a "no boot drive" error after you install a second drive with BIOS set to RAID.

As for the OS on the SATA SSD, I understand that you just want to use it for storage, not for Windows/booting. Whether you image it first or not is your decision, but I'd err on the side of precaution.

When you install this SATA SSD in the XPS 8950, you probably will have to boot the PC via the F12 menu to select the NVME SSD as the boot drive. That will avoid any incompatibilities with the OS on the SATA SSD. Then initialize the SATA SSD using Disk Management. When you reboot normally after initializing the SATA SSD the PC should boot from NVME SSD and the SATA SSD will be available for storage.

NOTE: You don't need/want to change the Boot Sequence in BIOS setup. Windows Boot Manager should always be first in the Boot Sequence, regardless of what/how many drives are installed. 

I get you, I should have read your initial reply more carefully, I assumed those steps were to get the old SSD running as the main OS, my bad.

So once I have the bits and pieces I need, I also need to:

• Set the BIOS from RAID to AHCI (following your steps).
• F12 on first boot once the drive's installed so I can select the NVME to boot from.
• Once in windows, use disk management to initialise the drive.

"So assuming both drives go into the same space, that should be sufficient."

I could be wrong as I haven't looked inside yet but it looks like there's a caddy on the left and right side for two 3.5" drives in 8950.

Is it safe to assume Dell would have made the power connectors on the same cable long enough to reach both?

I'll also look at macrium before doing any of this. Do you think there's a high chance of something going awry? Any idea if this would mess up the warranty?

 And thanks again for your help.

Apologies for not relying with an update to this thread. I never did get around to installing the hard drives, just couldn't risk anything going wrong and it didn't sound as simple as every other PC I've owned. So I just bought a usb caddy for the 3.5 drive.

Not trying to persuade you or anything.  Just want to say that adding additional hard drives into the XPS 8950 is simple as every other consumer PC out there.

It was the die hard habits of the geeks on this forum may have scared you off with all the big words and heavy tech terms.  Also the over concern, they were trying to cover all other processes adding up to an overwhelming task.

It's probably not the task for a first time PC user.  But if you have worked inside a computer before, it's relatively the same as other machines (as you have known), just mount the hard drive and attaching a couple of the cables.  Same for setup, creating partition and/or formatting the drive and it will be ready for your usage.

@HP9000258​ Open the side and there is no second caddy, and the power cable does not reach the secondary drive position.