My OS is on 2 disks. I have /boot as a RAID1 partition (md0). The rest of the disks are RAID1 (md1). LVM on md1, 2 logical volumes "/" and swap. I have never had any problems with the 2 boot disks and OS on LVM. My big array (md2) is not LVM. I never changed anything related to LVM, so it never really helped me in any way. I installed using RedHat 9.0. It was very easy to install/configure a RAID1 LVM setup. Guy -----Original Message----- From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of Derek Piper Sent: Thursday, January 13, 2005 4:23 PM To: linux-raid@xxxxxxxxxxxxxxx Subject: Re: combining two raid systems Maarten, I'm curious as to how you get on with LVM. I've been looking around and have seen that LVM seems to be a Bad Idea to run it on the root FS, and devfs seems to be scary also, so I wasn't going to even attempt any of that. I know Robin Bowes mentioned he uses LVM in that way, to 'carve up' a large RAID array. I'm curious if other people do that too and if they've had any problems. I'm not even sure of the maturity of the LVM stuff, anyone got any words of wisdom? Derek /still yet to get his feet wet in the whole RAID thing On Thu, 13 Jan 2005 21:27:07 +0100, maarten <maarten@xxxxxxxxxxxx> wrote: > On Thursday 13 January 2005 20:40, Bob Hillegas wrote: > > Set the sequence of hard drives to boot from in BIOS. Once you combine > > drives on single server, the drive designations will probably change. > > Need to figure out which sdx to put at the top of list. > > No, that's perfectly handled by the autodetection. My drive ID are reassigned > all over the place (of course) but that goes well. > > > Depending how you assemble array, you may at this point also need to > > tweak config file before you get the right drives assembled. > > Yes but as I said the config is only read when all the assembling is done so > that won't help much. (chicken and egg problem) > > > Introducing new SCSI devices into the chain is always interesting. > > Indeed. > > But I think I'm on the right track now anyway; I did --zero-superblock on the > unwanted md0 and md1 drives, and rebooted. At this point something > interesting happened: md1 now indeed was the right array (from system 1). > Md0 however was still from system 2. So I gathered from that that the SB also > 'knows' which md device number it has so I had two md0's that clashed. > Knowing that I took the risk of fdisk'ing the drives from 0xFD to 0x83 and > that helped: I'm now booted into my system 1 OS drive. > > I'll check if everything works now... gotta do stuff with LVM still at least, > and tweaking the mdadm.conf. > > Maarten > > > BobH > > > > On Thu, 2005-01-13 at 13:17, maarten wrote: > > > Hi, > > > > > > I'm currently combing two servers into one, and I'm trying to figure out > > > the safest way to do that. > > > > > > System one had two md arrays: one raid-1 with the OS and a second one > > > with data (raid-5) It is bootable through lilo > > > > > > System two had 9 arrays, one with the OS (raid-1) two raid-1's for swap, > > > and 6 md devices that belong in an LVM volume. This system has grub. > > > > > > All md arrays are self-booting 0xFD partitions. > > > > > > I want to boot off system one. I verified that that boots fine if I > > > disconnect all the [system-2] drives, so that's working okay. > > > > > > Now when I boot I get a lilo prompt, so I know the right disk is booted > > > by the BIOS. When logged in, I see only the md devices from system two, > > > and thus the current md0 "/" drive is from system two. Now what options > > > do I have ? > > > > > > If I zero the superblock(s) (or even the whole partitions) from md0 of > > > system 2, it will not boot off of that obviously, but what will now get > > > to be md0 ? It could be the second array from system 2 equally well as > > > the first array from system one, right ? > > > > > > I could experiment with finding the right array by using different kernel > > > root= commandlines, but only grub gives me that possibility, lilo has no > > > boot-time shell (well, it has a commandline...) > > > > > > Another thing that strikes me is that running 'mdadm --detail --scan' > > > also only finds the arrays from system 2. Is that expected since it just > > > reads its /etc/mdadm.conf file, or should it disregard that and show all > > > arrays ? > > > > > > Upon first glance 'fdisk -l' does show all devices fine (there are 10 of > > > them) > > > > > > I think (er, hope, actually) that with mdadm.conf one could probably > > > force the machine to recognize the right drives as md0 as opposed to them > > > being numbered mdX, but is that a right assumption ? At the time the > > > kernel md code reads / assembles the various 0xFD partitions, the > > > root-partition is not mounted (obviously) so reading /etc/mdadm.conf will > > > not be possible. > > > > > > I'll start to try out some things but I _really_ want to avoid having an > > > unbootable system: for one, this system has no CDrom nor floppy, and even > > > more importantly I don't think my rescue media have all neccessary > > > drivers for the ATA & SATA cards. > > > > > > Anyone have some good advice for me ? > > > > > > Maarten > > -- > > - > 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 > -- Derek Piper - derek.piper@xxxxxxxxx http://doofer.org/ - 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 - 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
