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inf3rno
Asked: 2017-08-01 06:17:45 +0800 CST

Is every onboard RAID fake RAID?

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I bought an MSI C236M workstation. It claims that it supports RAID 0/1/5/10. How can I decide what kind of RAID this is? Is it always "fake" RAID, or is there any chance that it is a true hardware RAID?

To my understanding it is better to use a software or a true hardware RAID, than these fake RAIDs coming with the motherboards... https://serverfault.com/a/522346/101323

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3 Answers

  1. Best Answer

    On almost all lower end motherboards on-board RAID will be "Fake" raid. It is possible however to get a motherboard with a dedicated hardware RAID controller. For instance a lot of Supermicro boards come with a dedicated RAID controller built onto the board.

    As already mentioned, yours has the Intel C236 chipset which comes with "Intel Rapid Storage Technology". I came across a system with this not too long ago and was bitten by the fact that the system had self-upgraded to Windows 10, which the management software was not supported on. The utility would not run and this controller has no real BIOS interface where you can manage the array like most hardware controllers. The Intel RAID format is fairly consistent and supported by Linux tools, so I tried to rebuild using that but gave up in the end.

    It's partly down to personal preference, but I would always choose software RAID (i.e. provided by the OS) if possible over Fake Raid, primarily for the following 2 reasons -

    • Moving the disks to new hardware will normally 'just work'. You're not going to have to find a system with the same motherboard or fake raid chip.
    • Managing the array can be done with the tools in the OS, rather than relying on continued support for software which is usually badly supported in the first place. In most cases it's also trivial to rebuild the array by simply connecting the disks to a different system running the same family of operating system or booting of a live CD.

    (Or course this mainly applies to Linux/Unix operating systems that have mdraid/ZFS/etc. Not sure of the current status of RAID in Windows - especially that which can be booted from?)

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  2. "Fake RAID" is nothing more than a software RAID done via a proprietary binary driver/blob. Any cache-less on-board RAID controller is a (near useless) fake RAID, made gluing together a SATA/SAS controller and said opaque driver.

    Its lone advantage over "pure" software RAID is the ability to present a single device for BIOS booting. Its disadvantages are much bigger, mainly:

    • you run untrusted code in the critical I/O path;
    • low compatibility with other boards.

    With such a controller, I generally disable RAID functionality and I use software RAID on the physical disks, basically using the SATA/SAS controller as is.

    You can argue than even "hardware RAID" cards really are nothing more than a specific software running on proprietary hardware, and in a sense this is very true. However, good RAID cards have a critical features: a powerloss-protected writeback cache, which greatly increases random writes performance and parity-based RAID speed. For more information, give a look here

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  3. Your question is malformed.

    You're operating under the assumption there is such a thing as hardware RAID, and the big lie the industry wont tell you, is that there is no such thing as hardware RAID.

    Traditional RAID is a hold over from the past where hardware was not fast enough and software was not advanced enough to do the job, so a second dedicated computer was used to manage the RAID. This is what people call a "RAID card".

    With hardware getting faster and OSes getting more advanced things like ZFS or BTRFS came along to take over the job.

    Your chipset is no different, it has software on it that manages striping or mirroring your disks just like a "hardware" RAID card has software or ZFS or BTRFS.

    Now the RAID cards people speak of do have advantages, they have read and write cache to improve performance and battery backup to protect from lost writes to the disk if there is a power loss. Similarly ZFS and BTRFS can have a cache disk (usually an SSD or NVMe) and just leave it to the controller on the write cache device to handle power loss protection.

    Your setup however has none of that, so in that you could call it a less advanced RAID system. But it's still RAID, well RAID 0 is not RAID it's stripe, and RAID 1 is not RAID as such, it's a mirror.

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