m15 R4, switched from RAID to AHCI in BIOS, performance decrease

Question

Hi all,

I recently replaced my dead Alienware 15 R3 with a new M15 R4 laptop. The laptop came with a 1TB m.2 drive that was set to RAID mode in the BIOS. I'm not sure why Dell ships a single drive configuration set to RAID in the BIOS, but maybe there's a reason for this I'm not aware of.

I added a 2nd 1TB m.2 drive that Windows assigned D as the drive letter, but I have an external HD that I need to be D, so I tried to change the drive letter in Windows Disk Management. The process hung forever so I had to reboot. I tried once again to change the drive letter using AOMEI Partition Assistant, and again the process hung. While in this app, I noticed AOMEI was reporting both drives were failing SMART tests and to replace them immediately. I knew this was bogus and that maybe I should change to AHCI from RAID in the BIOS.

I followed a post to do this to ensure the machine booted successfully back into Windows. This process worked, and now changing the drive letter worked perfectly. AOMEI also no longer reported the drives failing their SMART tests.
Everything is working great except for the performance of my main 1TB m.2 drive. On the other hand, the performance of my 2nd 1TB m.2 drive improved. The drive is still as fast as I'll ever need it to be, but I wondered if anyone has some explanations for this.

Below are the CrystalMarkDisk 8 stats of both drives in RAID mode, and then in AHCI mode. Why did the peformance decrease in some areas but improve in others? Because of the AHCI driver? Should I try switching back to RAID mode now that I have the drive letter changed? Another thing to mention is the transfer rate between the 2 drives improved greatly after switching to AHCI mode. Sorry for the long post, but I wanted to try and provide as much detail as possible.

RAID MODE Stats (Drives are not in an actual RAID just to be clear)

AHCI MODE Stats

Thanks all for your help!

crimsom · Accepted Answer

Hi @Rygar76 for systems that have NVMe drives, Intel says the BIOS RAID setting is enabled so that the M.2 NVMe drives can have RAID configuration at some time in the future. SATA drives can also be used because BIOS RAID setting also includes AHCI, for systems that have NVMe slots and SATA bay.

The old Alienware 15 R3 Storage can have NVMe and SATA drives, and BIOS RAID setting is enabled.

The new Alienware m15 R4 Internal slots are all M.2 PCIe NVMe, and BIOS RAID setting is enabled.

The new Alienware m15 R4 should not have BIOS SATA/AHCI setting enabled.

AWX17 · Accepted Answer

Yes. RAID-0, aka, Striping, aka, dividing all data across 2 drives is useless. 5% gain at most.
You DOUBLE your chances of COMPLETE, CATASTROPHIC failure if EITHER drive fails.

Now, RAID-1, aka, "Mirror" of your boot-drive, WAS sometimes used in big servers to protect the boot-drive. But that was years ago, with mechanical hard-drives.

So, I upgraded my X17 immediately to a Samsung980Pro M.2 PCIe4. 7000Mb/s. Fantastic.
First, create a bootable USB flash-drive for your Dell System using the Dell USB boot-drive utility.
Second, replace SSD, with your new drive. Change BIOS to AHCI.
Third, re-install Win11/10 by booting up with the Flash-Drive you just created.
I use Win11. WAY better than Win10.
This will create all the original Dell partitions on your new drive. As well as will install the latest version/patches of Windows/Drivers/Image partitions.

DO NOT, try to re-install Windows from BIOS back onto your new drive. It will not work.
A HARDWARE/BIOS Raid-5, not OS/software RAID-5 is the cat's meow. 50-70% performance gain, easy...and on a big server, you can just swap out the bad drive, WITH THE POWER ON, and ALL users continue to access the system...while the RAID-5 controller automatically rebuilds the data on the new drive when you insert it. NO SHUTDOWN.
But RAID-5 requires 3 identical drives/interfaces.
RAID-0 is not a toy that should be used on any system. The risk is to great. Gains are too small.

crimsom · Answer

Hi @Rygar76 there are different types of RAID mode, and this includes single and multiple drive configurations. RAID is inherently unreliable, and is no substitute for back-up drives as part of disaster recovery plan, if original drive cannot be recovered.

Please visit Disk Management to check that M.2 drives have the modern GPT partition format (not MBR) with enhanced reliability, security, etc. and that BIOS boot list option UEFI is enabled for fast boot.

Rygar76 · Answer

Thanks for the replies all. I checked in Disk Management, and both m.2 drives are GPT partitions. I have no plans to ever use an actual RAID now or in the future, so I think I will just leave BIOS set to AHCI, and deal with the minor decrease in performance. While it decreased my main drive performance, you can see in the screenshots that switching to AHCI mode greatly increased the performance of my 2nd m.2 drive, so I'm happy with these results overall.

My closing thoughts are I feel Dell should consider shipping laptops with a single drive in AHCI mode to give the user the option to switch to RAID in the future if they so desire. I can't imagine using an actual RAID on a laptop is that popular of a configuration, but I could be wrong. Also by shipping in RAID mode and then adding a 2nd drive, the user cannot change the drive letter. For most this isn't a big deal, but for me I'm reinstalling programs that use project files and resources that all reside on the D drive from my old Alienware, hence why I wanted to change drive letters. My 2nd 1TB m.2 is now drive letter Z, and my external is now D to match how I used it on my old Alienware.

Perhaps doing a fresh install as suggested while in AHCI mode might provide better results, but for now everything is working as needed, and the main drive is still plenty fast.

Thanks all for your help!

crimsom · Answer

Hi @Rygar76  you have made a simple job very complicated. Dell predominately use Intel CPUs and will always enable BIOS RAID setting. It is your choice to mess around with your Alienware m15 R4 laptop, but it is not reasonable to advocate that Dell or other users adopt your curious recommendations.

Rygar76 · Answer

I completely agree with you. What if someone adds a 2nd drive and wants to change the drive letter? I would imagine this scenario is far more common than anyone actually using a RAID configuration on their laptop. Changing drives letters is not not possible in RAID mode and I think this will only cause headaches for a lot of people as it did with me. Changing drive letters is something I do quite often, so I would still like to know why Windows hangs when trying to change drive letters when in RAID mode.

Also nobody has commented on the performance changes on my drives before and after the change.

Thanks for your time.

Rygar76 · Answer

What a pompous response. I never once made any recommendations or advocated anything. I only presented what I found and asked questions. People like you are the reason I refrain from posting 90% of the time.

AWX17 · Answer

Sorry, I was agreeing with you. There is no reason for a laptop/server to be in a RAID-0 configuration.I was surprised my X17 came in that config. Raid0 was always useless. Way back in 1990.

AWX17 · Answer

Yep. I read them very carefully....and it didn't surprise me that your second drive had a big performance jump when taken off RAID.
Keep in mind ALSO, that, keeping it in a RAID configuration WILL waste clock cycles, as the system now has to realize, and calculate, that the drives are NOT RAID'ed. Therefore, back to a regular AHCI "type" of data storage/transfer. Yes, I am assuming your are absolutely correct about being able to change your drive letters. We've been assigning drive letters since the 80's. It's very basic and fundamental to the operating system. (pompous? haha...perhaps...more like THICK callous from banging my head against the wall since 1990
Trust me on Dell's USB Flash-boot drive though...it's very good.
You must have your modem password handy though, before you begin.

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m15 R4, switched from RAID to AHCI in BIOS, performance decrease

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