Tracy Reed said:
In what way does Linux need to know it is doing software RAID to boot from a mirror? It boots the kernel, grabs the initfs from one of the drives, assembles the RAIDs, pivots root to whatever I tell it, usually /dev/md0 which is just another block device to the OS. Perhaps what you say is true if you want to RAID 5 the boot drive but I would avoid that situation precisely to avoid such complications.
the BIOS doesn't know about the raid, so if the drive the BIOS is trying to boot from is dead, how do you get the bootloader to startup to even find the kernel?
hardware raid makes the mirror look like a single drive to the BIOS and so even if one drive is dead, the BIOS will still find a drive to boot from.
David Lang
On Mon, Jan 02, 2012 at 10:27:50PM -0500, Brandon Allbery spake thusly: > The hardware/software distinction, in practicality, is "does the OS need to > know that it's actually doing RAID?" Because there are a lot more failure > modes if it does, and more complex situations (as already mentioned, boot > drives are a major one). In what way does Linux need to know it is doing software RAID to boot from a mirror? It boots the kernel, grabs the initfs from one of the drives, assembles the RAIDs, pivots root to whatever I tell it, usually /dev/md0 which is just another block device to the OS. Perhaps what you say is true if you want to RAID 5 the boot drive but I would avoid that situation precisely to avoid such complications. -- Tracy Reed http://tracyreed.org Digital signature attached for your safety.
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