On 21/11/17 20:42, Lew Wolfgang wrote:
What's the betting the firmware in said contoller is a cut-down linux/mdadm combo? :-)
There seems to be a common signature element between the LSI controllers and mdadm. Which came first?
Not a clue :-) It wouldn't surprise me if LSI came before mdadm - certainly early linux raid didn't have a superblock (look at the info on the legacy --build option to mdadm :-) Mind you, hardware raid might have made the same assumptions and not had a superblock. But my guess is that the hardware controllers got it first, the linux guys looked at it and said "this is a good thing", and rather than re-invent the wheel, pinched most of it. Thing is, there are several "official" raid standards, which linux can handle, but it prefers to do its own thing. And linux raid has evolved through three or four generations. Gen 1: the --build era. Can't remember the name of the config file, arrays are assembled in user space. Gen 2/3: the version 0 superblock (I only know of v0.9), and the raid array filesystem code type. I don't know how all this lot fits together - it's all obsolete - but the crucial features were that because the fileystem doesn't know about the raid, you can access the filesystem directly without the raid (read-only only of course). Then once the raid is up and running you (re)mount the raid as root read/write. Gen 4: the version 1 superblock. All the version 1 superblocks themselves are identical, it's only the location that changes. 1.0, like 0.9. is at the end of the device so you can access the filesystem outwith the raid and boot off it. Note that the raid partition type is now meaningless, and the kernel doesn't know anything about v1 superblocks, so all raid management MUST be done in userspace. V1.1 stores the raid at the start of the device. This is not usually considered a good idea because, especially if you give a disk rather than a partition to the raid, a lot of things stick their metadata at the start of the device (fdisk, gdisk for example) and it's too easy to trash it by mistake. Both v1.1 and v1.2 reserve a chunk off space at the start of the device, just that v1.2 stores the superblock 4K into device. Cheers, Wol -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org