Chris Croome wrote: > Hi > > On Fri 11-May-2007 at 09:38:22AM -0400, Ross S. W. Walker wrote: > >>> The entire use all four disks for /boot makes no sense if two disks >>> belonging to the same mirror for the lvm go down. Please stop this >>> nonsense about surviving everything to no benefit. You can have >>> three disks fail and still have a working /boot. For what? >>> >> I think the idea of the 4 partition raid1 was more of, what else is he >> going to do with the 200MB at the beginning of each disk which he has >> because of partition symmetry across drives? >> >> Makes sense to just dup the partition setup from one to the other and >> now with grub and a working /boot on each disk the order of the drives >> is no longer important, he can take all 4 out, play 4 disk monty, slap >> them back in and the system should come up without a problem. >> > > FWIW this is what I did with the last server I built which had 4x500gb > drives -- a RAID 1 /boot on 4 drives. The trick for this is to edit your > grub.conf so that you can boot off any drive and run grub-install on all > 4 drives, also you have to remember to manually edit your grub.conf > after each kernel upgrade to add the 3 extra disks: > > title CentOS (2.6.18-8.1.1.el5xen) Disk 0 > root (hd0,0) > kernel /xen.gz-2.6.18-8.1.1.el5 > module /vmlinuz-2.6.18-8.1.1.el5xen ro root=/dev/VolGroup00/Root > module /initrd-2.6.18-8.1.1.el5xen.img > title CentOS (2.6.18-8.1.1.el5xen) Disk 1 > root (hd1,0) > kernel /xen.gz-2.6.18-8.1.1.el5 > module /vmlinuz-2.6.18-8.1.1.el5xen ro root=/dev/VolGroup00/Root > module /initrd-2.6.18-8.1.1.el5xen.img > title CentOS (2.6.18-8.1.1.el5xen) Disk 2 > root (hd2,0) > kernel /xen.gz-2.6.18-8.1.1.el5 > module /vmlinuz-2.6.18-8.1.1.el5xen ro root=/dev/VolGroup00/Root > module /initrd-2.6.18-8.1.1.el5xen.img > title CentOS (2.6.18-8.1.1.el5xen) Disk 3 > root (hd3,0) > kernel /xen.gz-2.6.18-8.1.1.el5 > module /vmlinuz-2.6.18-8.1.1.el5xen ro root=/dev/VolGroup00/Root > module /initrd-2.6.18-8.1.1.el5xen.img > > If I had read this thread before I set up this machine I'd have used > RAID 6 from the rest of the space, but I used RAID 5 with a hot spare, > with LVM on top of that. > > Before the machine was moved to the colo I tried pulling disks out while > it was running and this worked without a problem, which was nice :-) > > Chris > > Chris, I didn't have to install grub on any of the other volumes, and the server seemed to do well after drive failure (I pulled out drives 1 and 3). In my opinion, neither raid5 or raid6 makes sense with 4 drives, as you will get the same amount of space with raid10, but much better performance and availability (although raid6 is supposed to withstand 2 drive failures, in my tests it has not done well, and neither has raid5). As you might've read from the thread, if you want to put the / volume on the raid10, it will not be possible during the install, but you can set up 2 raid1 volumes, and do an LVM stripe across them which should yield comparable performance. Russ