Hello, On Fri, Jul 19, 2013 at 12:02 AM, Martin Wilck <mwilck@xxxxxxxx> wrote: > > Fake RAID uses a part of every disk to record information about the RAID > arrays. This is called meta data, and your BIOS uses it for setting up > the drives. > > Under Linux, first you need a low level SATA or SAS driver that detects > your physical drives, e.g. the ahci driver. > > md can then detect the DDF meta data on your disk just like the BIOS, > assemble the array(s), mirror the data, and do other RAID operations. > Yes, but my question is about how md cooperate with the BIOS in this case ? > Distributions can set this up automatically. Currently most distros > don't do this for DDF (they do it only for fake RAID using the Intel > Matrix (IMSM) format). For DDF, for historical reasons, most > distributions will setup a mapping using dmraid (device mapper based > mirroring). That will also basically work, but it isn't a > fully-functional RAID implementation such as MD. The magic to set up > either MD or dmraid automatically as disks are detected is hidden in the > distro's udev rules, and possibly in the distro's installer logic. That's true, and I'm in the process of "fixing" the default setup (dmraid, done during my distro installation) with MD. > > The DDF functionality in mdadm is not quite as complete as for other > meta data formats, in particular IMSM. I am currently working on > improving it, because I want to use just a similar fake RAID under Linux > as you, and fully benefit from MD's feature set. That's an interesting information thanks. > > Before doing real work with DDF on your system, make sure that the BIOS > still detects your drives correctly after MD/DDF has written its meta > data (this happens when an array is shut down, for example). > There is a small but non-zero risk that the BIOS may reject the > configuration as written by MD. The same may happen e.g. for a Windows > fake RAID driver. That's a good idea. Are there any procedures described out there that I could follow to test MD DFF ? > > If you experience any problems, be sure to report them here. > I will. Thank you. -- Francis -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
