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I have an 8 bay SATA/SAS LSI MegaRAID controller and have to mount a set of drives that were assembled RAID 6 by mdadm on a non RAID controlled other device (both supermicro).

Is it possible to configure the LSI MegaRAID to just mount the drives so I can assemble the RAID using MDADM. It doesn't recognise the virtual disk that spans the set and I can't see a way to "just mount" them.

I don't want to lose the info on the disks so can I do this or can I only mount them on a non RAIDed device?

Is the reverse also possible? To mount a MEGARAID set on a non RAID controller and assemble using mdadm? Thanks

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Firstly you should be able to configure the LSI controller to allow the 8 disks to just be passed-through to the BIOS/OS in 'JBOD' mode, or at worst configure each disk as a single-disk RAID 0. This should allow your OS to see the disks and hopefully reassemble the software array.

As for the other way around - do you mean can you take a LSI-built array and connect it to a 'dumb' disk controller, which would inherently present the disks through to the machine as single disks and then somehow stitch the array together? If so then I highly doubt it, it'd see the disks but almost certainly wouldn't know how to deal with them in the exact same way as the LSI controller.

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  • Thanks Chopper3 - I'll try JBOD.
    – ChrisMinto
    Dec 2, 2023 at 16:31
  • The other way around was meant that if I have an LSI Raid 6 set of disks for example, can I mount them in my other SM that is just a controller and not a HW RAID and then mount the RAID as a virtual disk in Linux?
    – ChrisMinto
    Dec 2, 2023 at 16:32
  • Yes, Linux MD RAID should recognize on-disk data structures made by LSI MegaRAID. But test this scenario first to be sure. Dec 2, 2023 at 16:48
  • So I have the LSI MegaRAID 2108 - the SM manual for it suggests you can't the only way is for the drives to each be RAID 0 (on their own) before you do it - so in my case for a RAID set from mdadm previously I think doing this is going to ruin the data... supermicro.com/manuals/other/…
    – ChrisMinto
    Dec 2, 2023 at 16:53

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