Ken Mink wrote: > If I'm wrong about this, I know someone will correct me. > > I just want to review so you can correct me on the setup. You've got 8 > drives; 1 for /boot and swap and 7 in a RAID5 array. You've been able to > partition for /boot and swap and have successfully created the RAID5 array > which is /dev/md0. Now you want to carve up /dev/md0 for filesystems and/or > other volumes? >
It seems like a waste to use 1 whole drive for /boot (I am assuming they are identical drives). I actually don't know what the current state is as far as grub/lilo booting from RAID5, but I am pretty sure they can boot from a RAID 1. There is nothing preventing you from running a crazy 8 drive RAID 1 as your boot partition. That way you can install lilo/grub on each drive and it will be able to boot no matter what happens. > /dev/md0 is logically the same as a single partition. The word logically is > a clue for you. You need to use LVM(Logical Volume Manager) to create > logical volumes inside md0. You can then use the logical volumes for > filesystems and such. > Technically, there is nothing preventing him from creating a file system directly on top of /dev/md0. > If you're unfamiliar with logical volumes, they're incredibly useful and > allow for all sorts of disk configurations. I don't have a good link for a > guide. Maybe someone else could provide one. > LVM rocks. However, I think it is (usually) a reasonable idea to create more than one md device on each set of drives. Slicing a set of drives up gives you more flexibility if you want to add or remove drives from a RAID 5. I can probably explain better by example. If you partition the raw drives into, say, 4 partitions. /dev/md0 being a RAID 5 of the first partition of each drive, /dev/md0 the second partition, up to /dev/md3. This gives you 4 RAID 5 arrays. You can then take each of the md devices and add them all to the save volume group. So far, this seems pretty pointless. Lets say this was a 4 drive array. Next year, you decide to add 2 more drives... In this case, as long as your VG is 25% empty (or can be made 25% empty), you can manage to extend the RAID 5 from 4 drives to 6. First, you'd partition your 2 new drives to match the other 4. Then you would remove 1 of the md devices from the VG and destroy that md device. You would then recreate that md device with 6 partitions instead of 4, and add it back to the VG. Repeat 3 more times and you're done. I don't know how clearly I have explained, and I would be more than happy to clarify anything :). > I hope this was helpful and correct, > Ken Me too :) Pat
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