On Sunday 17 May 2015 12:48:58 Nuno Magalhães wrote: > I want to use mdadm to create a RAID1 with 2 SATA disks. From what i > gather, i'll need (bootable) 0xFD partitions, i'll use full disk for > them and no separate /boot (unless required). Is GPT required or can i > stick to MBR? Is fdisk safe? Seems usable to me.
Use this guide: https://wwwold.gentoo.org/doc/en/gentoo-x86+raid+lvm2-quickinstall.xml > Is 0.90 metadata mandatory for RAID1? What's the recommended version? You need 0.90 metadata for any volume that needs to be bootable, unless you use what Dale calls an init thingy. I don't do that, and this is my setup: /boot on /dev/md1 = /dev/sd[ab]1 in RAID1 with metadata 0.90. / on /dev/md5 = /dev/sd[ab]5 in RAID1 with metadata 0.90. [the rest] on /dev/md7 = /dev/sd[ab]7 in RAID1 with metadata > 1.0. > I've seen manuals that use mknode, but discovered that mdadm --create > will create a /dev/md for me. I didn't know that. Interesting. > (Later i want to get rid of systemd-udev and use eudev instead.) I use openrc, not systemd. It still works well and has less complication - and less typing! > Also, why so many tty* and similar in /dev? Is there a way to make it > less crowded? Just a whim... I tried removing them but found they'd been re-created after the next boot. Ho hum. > Does GRUB2 (rather grub2-install) handle well RAID1 stuff or does it > get confused? Don't know. I use legacy-grub. The last I looked, grub-2 couldn't handle the choice of kernels I have. > What's the difference between dodmraid and domdadm? I don't want to > use fakeraid, so is it safe to just use domdadm? I think so, yes. As far as I know, dmraid is fake raid. > Then i want to use LVM on the /dev/md and setup my / in an LV. This > seems straightforward (as far as creation goes). Any tips here? I > remember you could tune LVM LVs to the underlying RAID stripe. I just followed the quick-installation guide. > I intend to use XFS for /. Incidentally, if i later decide to "fork > out" /usr (or some other subdirectory) into it's own LV, is it "just" > a mater of copying its contents and updating /etc/fstab? Or should i > just do it now and expand the LVs if later required (especially if i > want to use different filesystems)? I can't help you with XFS. I know that ext4 in an LV in a VG in a PV on RAID1 works reliably, even though it does look complex when I write it like that. > The problem will be (has been) getting it to boot. > > If i have 2 kernels in /boot, shouldn't grub2-mkconfig generate 2 > entries in the GRUB boot menu (not counting the recovery entries)? > > I read somewhere that genkernel is a bad choice for creating the > kernel because it un/sets a CONFIG_ flag that interferes with RAID/LVM > (sorry, i should've noted where/what). I use make menuconfig anyway, > it's fun. I do use genkernel to create the initramfs, i'm assuming > "genkernel --lvm --mdadm --bootloader=grub --install initramfs" would > suffice? Again, legacy grub here. But if you're using an initramfs, from what I've seen you don't need to specify metadata 0.90. --->8 > While the Handbook is awesome, it doesn't cover this and all the > information i find is either outdated or conflicting. I reinstalled yesterday while following the guide I cited. Damn. I've just checked and something has renamed my /dev/md7 to /dev/md127. Again. It's just too bad. I shall have to stop it when I get a quiet moment and reassemble it into /dev/md7. Actually, I know what caused it but I didn't notice at the time. HTH. -- Rgds Peter
