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So I recently set up Intel RST RAID on my Gigabyte z77‑d3h with UEFI firmware. The UEFI system recognizes the new RAID array instead of two disk and load bootx64.efi from the array.

The RAID array is a Windows/Linux dual‑boot system. I had no problem with Windows, as it simply recognized the RAID array instead of two disks (I didn’t had to reconfigure or install anything). The individual disks don't even show up in devmgmt.msc.

However, in Linux I have still /dev/sdaXX and /dev/sdbXX (where XX is the partition number). Only /dev/dm‑0 is created automatically by the kernel. But there aren’t sub block devices for partitions because dmraid knows nothing about gpt.

I tried to use software RAID. However, even for simple mirroring, mdadm require using metadata which won’t be understood by Windows®.

So how do I use an fake RAID array in Linux with GPT?

user2284570
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  • Please specify the exact Gigabyte motherboard. You are assuming you have hardware raid but as pointed out in an answer, this is very unlikely. – ChrisInEdmonton Jan 11 '16 at 14:13
  • @ChrisInEdmonton : see my [edit](http://superuser.com/posts/1024695/revisions). – user2284570 Jan 11 '16 at 14:55
  • It is indeed the case that the Z77 chipset does not do hardware RAID, only software RAID (aka 'fakeRAID'). That's fine, for RAID0 and RAID1, you almost certainly don't care (and may not for RAID5), but hopefully this will guide you into setting up the fakeRAID in Linux. – ChrisInEdmonton Jan 11 '16 at 14:59

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Do you have a hardware raid? or a software assisted hardware raid(also called soft raid). manufacturors can be pretty deceptive about what they actually sold you in this space.

UEFI sees the first FAT partition and boots from it, and the configuration might simple mirror that partition on both disks. Just because a efi partition is seen don't prove you have raid it might simply be two mirrored filesystems.

On boot windows will load a driver and let the driver handle the raid ie it's software raid in all but name but windows don't always show this to the user. Linux tend to not ship soft raid drives in "the mainline tree" even when the manufacturers supply them because they have historically been problematic, and rarely actually provide benefits over the more optimized dmraid module.

Some vendors supply linux drivers for softraid controllers but it's one of the few exeptions where you actually need to go and download drivers on linux.

The typical difference here is that softraid controllers tend to depend on CPU offloading which makes them cheaper and usually slower then the full raid controllers you find in better server class hardware.

dudsen
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  • Did you pay attention to the question title and tags ? Or do you want me to add the controller is an Intel one ? ᴜᴇꜰɪ doesn’t use exfat. Your answer is full of wrong things. – user2284570 Jan 11 '16 at 13:44
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    exfat is the closed standard analogue to the FAT32 filesystem the UEFI system stores boot64.efi on that script/application is what defines how the system is booted. as long as that application contains the right information the OS will load. – dudsen Jan 11 '16 at 14:05
  • Yes but no uefi firmware can read exfat. – user2284570 Jan 11 '16 at 14:17
  • It have to read FAT32 it's in the specs. But the firmware doesn't actually read the OS's filesystem it just runs an executable with just enough capabilities to bootstrap a kernel. – dudsen Jan 11 '16 at 14:23
  • ꜰᴀᴛ32 or ꜰᴀᴛ16 isn’t exfat. I compiled my kernel as an uefi application which is loaded as a windows installation by the windows® boot manager. – user2284570 Jan 11 '16 at 14:57
  • Are there any way to get partition block devices for the automatically created `/dev/dm-0`? – user2284570 Jan 11 '16 at 16:00
  • you probably want to take a look at this http://www.intel.com/content/www/us/en/intelligent-systems/software/rst-linux-paper.html – dudsen Jan 11 '16 at 16:08
  • which require flash player. – user2284570 Jan 11 '16 at 18:39
  • "UEFI sees the first FAT partition" - You mean FAT32? Please be specific little details like that actually matter. – Ramhound Jan 15 '16 at 20:42