Yesterday I was feeling empty, and I wasn't sure why. I realized later in the day it was because there had been no batch of daily FC3 errata. Imagine my relief this morning when I logged in and saw the pulsing red panel applet.
There was a new update for the dmraid package with a fairly substantial changelog and nice surprise to boot. The changelog included:
- added NVidia metadata format handler (#130324)
This is neat. It mean that dmraid can now handle and use the Nvidia Nforce 3&4 chipset created RAID volumes.
My home World of Warcraft system has mirrored drives handled by a Nforce 4 motherboard.
With this dmraid change, the pieces are falling into place for me to be able get a Fedora Core (possibly Rawhide) install recongizing and using the motherboard built RAID volume instead of seeing the two drives separately.
The dirty little secret with onboard RAID and sub $100 RAID adapters is that they don't actually do any RAID processing themselves. The exist to hook into the BIOS and allow booting off of the RAID volume. The RAID configuration is stored in a little chunk of metadata at the begining of drive members.
The RAID functionality, ie writing to both drives at the same in the case of mirroring, or parity calculations are handled within the operating system driver.
If an operating system is installed without specific RAID drivers then the operating system will see all the individual drives. If the RAID support gets accidentally turn off in the BIOS then the operating sytsem will still likely boot and see all the individual drives. If the operating system continues running then it will just write to one of the drives, and the RAID volume becomes desynced.
If multiple operating systems are installed, then they need to all support the RAID meta data and see the volume as a single entity as instead of multiple drives.
True hardware RAID volumes don't have this problem as it is impossible for any operating system no matter the driver or BIOS state to see the individual drives.
