SM951 as OS boot device information

TimH wrote: I do have 3x256GB 951's. I have reset the stripe size to 128k and I am doing much better. I was also fighting a memory chip problem at 64GB DDR4. I've fixed that for now but I need to trouble shoot and see if the chip is bad or if the board is bad, or if the UEFI has an error.  That will be my next effort. I do feel that the 16k size Is not optimal for the RAID M.2 cards. My next question would be if I bought 3 PCIE adapter cards for the M.2 cards and put them in PCIE slots I wonder if my performance would increase. Hmmmm

I don't know either, in theory the performance should be the same.

I do know if you used three PCIe adapter cards, you would have four PCIe lanes left for a video card, if you could get it to work through the Z170 chipset.

IF the performance was better using the PCIe lanes in the CPU, it would not be very much and in real world usage you could not tell the difference IMO.

This is one SM951 in my ASRock Z97 board. It has one Ultra M.2 slot, but uses the PCIe 3.0 lanes in the CPU:




The third line with Seq, or Sequential single file speed is the one to mainly compare to your RAID 0 results. You can also see the 4K random speed is better, but that is due to no RAID here, which reduces 4K performance.

Thanks for your opinion on the stripe size question. Are you using your RAID 0 array as an OS drive? Regardless, do you think you can tell the difference in performance between the two stripe sizes? Please tell me your honest opinion, don't worry about what I'll think.

Thanks for staying with us after the optimal (?) stripe size was found. It seems someone else got what they needed and hit the road...

I have another bit of information about these RAID arrays that I'd say is rather important. But that is for another post. You'll be glad you're still here when you read it.

I learned something (the hard way) today about using PCIe SSDs in RAID 0, related to the settings in the UEFI that are necessary to allow their creation and usage. Or should I say, the preservation of the RAID 0 array.

One of those options is the RST PCIe Storage Remapping option, one option for each of the three M.2 ports, M2_1, M2_2, and M2_3, found in the Advanced, Storage Configuration screen in the UEFI.

I had never encountered this option in the past, since it did not exist until support for creating RAID arrays from PCIe SSDs was introduced in IRST by Intel. These options must be set to Enabled for each of the M.2 ports that have a PCIe SSD that is part of the RAID 0 array. The default setting is Disabled.

I wrote earlier in this thread that these options must be maintained in their Enabled state when using the PCIe SSDs in RAID 0. That is generally similar to maintaining the SATA mode as RAID when using RAID arrays.

But there are situations where options in the UEFI are reset to their default settings, such as clearing the UEFI (CMOS clear, BIOS clear), or after a UEFI update. RAID is not the default setting of the SATA Mode option, so must be reset to RAID after the situations that reset the UEFI options to their defaults. That is easily done by the user, I have done it countless times, and my RAID arrays of SATA SSDs always work fine as long as I reset the SATA mode to RAID before the PC boots the OS after the UEFI settings were set to their defaults.

With PCIe SSDs in RAID 0 we now have another set of UEFI option settings that are required for those RAID arrays, RST PCIe Storage Remapping . I decided to see what the affect of a UEFI clear, or simply setting RST PCIe Storage Remapping to Disabled, would have on the PCIe SSD RAID 0 arrays. That is, after a restart of the PC and going directly into the UEFI to reset the options required for PCIe RAID, SATA Mode and RST PCIe Storage Remapping.

So I did just that and restarted the PC and went directly into the UEFI. I checked the IRST Storage Utility option in the Advanced screen, and found my RAID 0 array of two PCIe M.2 AHCI SM951s (the OS volume with Win 10) had a status of Failed. I checked the Boot screen to see if the RAID 0 volume was listed as a boot device. It was not listed.

That of course was not good to see. I reset the two RST PCIe Storage Remapping options for my two SM951s to Enabled. I then saved and exited the UEFI, and went directly back into the UEFI.

Unfortunately, I found my RAID 0 array in the same Failed state. I had seen this once before when I had cleared the UEFI with a RAID 0 array of the SM951s used as a data drive, not as the OS drive. RAID 0 arrays have no redundancy, and cannot be recovered. I thought it was a fluke the first time the RAID 0 array failed, but now I had experienced it again. The only related change was the RST PCIe Storage Remapping option being set to Disabled.

I had to delete the failed RAID 0 array, create it again, and install Windows 10 again. That all worked fine, I'm using that PC now to write this post.

Don't forget the only change I made in the UEFI was to set the RST PCIe Storage Remapping options to Disabled, and restart the PC into the UEFI. A simple UEFI clear or UEFI update followed by the inevitable restart will cause the PCIe RAID 0 volumes to fail. Any data of the drives will be lost, as well as an OS installation.

How can we avoid this? I did not try this, but since we cannot simply remove the power source from M.2 SSDs like we can with SATA SSDs, we could (try) removing the PCIe SSDs from the board before a UEFI clear or update. After the UEFI clear or update, reset the RST PCIe Storage Remapping option settings to Enabled, restart the PC into the UEFI so the enabling of those options will be applied. After that, shutoff the PC, install the SM951s again, start the PC and hope it works. Or have a back up image of our OS installation and use it to restore our OS onto a newly created RAID 0 volume.

I don't know if a change to those UEFI options to fix this issue/situation is possible. Why the PCIe SSD RAID 0 array is so fragile that simply disabling the RST PCIe Storage Remapping option will cause them to fail, I do not know. IF I am missing the technique for preserving the RAID 0 volume when the RST PCIe Storage Remapping option is reset to Disabled, I'll be happy to learn what it is.

It may be possible that an update to the IRST driver and Option ROM can fix this phenomenon. SATA SSD RAID arrays survive fine if the SATA mode is not set to RAID during a UEFI reset or update. Of course SATA SSDs don't need the RST PCIe Storage Remapping option.

Sorry for the long story, but I wanted to explain everything clearly, since what happens between the resetting of those options and restarting the PC is invisible to us.

Morale of the story, be very careful with PCIe SSDs used in RAID 0 arrays, used as OS volumes. That is always true for SATA SSDs, and now more so for PCIe SSDs. I'd love to be missing the technique of keeping these RAID 0 arrays out of the failed state, but I don't see what it is.

Feel VERY FREE to prove me wrong!

Ronzer wrote: parsec wrote: Thanks for staying with us after the optimal (?) stripe size was found. It seems someone else got what they needed and hit the road... I did hit the road, I'm on vacation in France and wont have access to my desktop for a week.:)

OOPS... well that explains that!   I hope you enjoy your vacation!

We need as many SM951 RAID 0 users as possible posting their experiences here so we can learn as much about all this as possible. That is why I was disappointed you seemed to disappear.

TimH wrote: That's terrifying Parsec!!! Open in Google Docs Viewer Open link in new tab Open link in new window Open link in new incognito window Download file Copy link address Edit PDF File on PDFescape.com Open in Google Docs Viewer Open link in new tab Open link in new window Open link in new incognito window Download file Copy link address Edit PDF File on PDFescape.com I wonder if it would be worthwhile to clone the drive from time to time to a backup device so you don't have to start from zero each time a new bios update comes out from ASROCK or you have to clear the CMOS.

Yes it really is terrifying!!!    
RAID 0 arrays are considered dangerous anyway, given no redundancy and the loss of one drive (failure of the drive) will cause all data to be lost. But this new twist is nothing like I've ever seen when using SATA SSDs in RAID 0.

I've cleared my board's UEFI with RAID 0 arrays of SSDs as the OS drive many times, and have never lost the RAID 0 array. Same thing when updating the UEFI to a new or different version. As long as you reset the SATA mode to RAID before booting the OS, all is well. I've removed a set of SSDs in RAID 0 from a PC and put it back later, still worked fine.

What actually happens  to the RAID 0 array when the RST PCIe Storage Remapping options get set to Disabled, I don't know. All I know is the IRST utility in the UEFI shows that one of the SSDs "failed" and can't be recovered, so the only option is deleting the RAID 0 array. The so-called failed SSD is not broken in any way. I'm using it now in a new RAID 0 array with Win 10 installed again. The new RAID 0 array could be created without any other work besides deleting the RAID array.

Is it worthwhile to clone the OS to a backup drive? How about... required?

Guess who did just that? ME! Although installing Win 10 again took all of ten minutes from the very start to the first Windows desktop display on the monitor (less than four minutes once the "Preparing files..." screen was shown), and that includes entering the license key and me forgetting to put the IRST driver flash drive in the PC, it is still a pain to do.

Unless I'm missing something, like an option or setting in the UEFI, I don't know how to get around that situation. I don't know if the UEFI is at fault, or the Intel Option ROM, or something else. This is the first time we've had official support for RAID arrays of PCIe SSDs, so we should be prepared for issues. If this is a permanent limitation, it is a bad one. If a bug, it is a big one IMO and needs to be fixed.

How is your RAID 0 array working for you? I have some questions for you, just to verify if the way certain details are on your PC are the same as on mine. I'll do that in another post, coming very soon.

UPDATE: AsRock has come through and produced a new UEFI version, labelled 1.30B for the Extreme6/3.1.  With this, the M.2 SM951 is seen as a bootable device when installed in a PCIe x4 adapter card.