Hi,
I'm helping a friend setting up a website.
We use fysical server (with two equal harddisks of 500GB) from home.
I have some experience with Ubuntu and have recently switched to fedora.
I adviced using Fedora F16.
What I would like to do is:
- Create a RAID 1,
- Create LVM on this RAID
- Create some BTRFS partitions on this LVM

Why LVM and BTRFS? I want to isolate the partitions, so that filesystem running full has local effect (in one partition) only.
I had this working with Ubuntu 11.10 for a while. Latest friday I tried to create similar using Fedoira F16, but I ran into some issues:
- When I tried to create LVM PV on RAID device, An Error is displayed stating that RAID device can not be used with growable disks (or something).
- I worked around it using Ubuntu, but when I installed, only the first disk is bootable (e.a. when I remove te first disk no bootable partitions can be found.

Can you please advice:
- What is the best sollution for being able to boot degraded, and use flexible partitioning
- How should I configure this during installation

Seems to be a one man show. Well, I hope that this might help others.
I finally installed Fedora with good working SoftRAID.
How? Two caveats:
- There seems to be a bug in the installer with the MD Creation proces.
When you want to create the array a message is printed:
Only RAID0 arrays can contain growable members.
I can't seem to fix it, so I create the partition layout at forehand.
- There is a bug in the process for detecting MD metadata version.
Read this for more info: https://bugzilla.redhat.com/show_bug.cgi?id=750480

This is what I do:
- I boot using the Fedora 16 DVD (64 bit)
- I enter Rescue system
- I move forward untill I get a shell.
- I partition both disks the same
- Partition of 500MB
- Partition of the rest of the diskspace
- I create a SoftRAID on the first partitions (mdadm -C /dev/md0 -n 2 -e 0.9 /dev/vda1 /dev/vdb1)
- I create a SoftRAID on the second partitions (mdadm -C /dev/md1 -n 2 -e 0.9 /dev/vda2 /dev/vdb2)
- I wait until both arrays are build
- I create an LVM Fysical device on md1, build Volume Group and Logical VOlumes
- I partition /dev/md0 using ext4 and all the others as I wish
- I reboot again using the Fedora 16 DVD (64 bit)
- On the Install section I press tab and enter ' updates=http://dlehman.fedorapeople.org/pdates/updates-750480.3.img' at the end of the line.
- In the disk layout page I choose all the partitions and configure their mount points (/dev/md0 = /boot).
- In the next page I choose that the boot sector is written to the disk (/dev/vda in my testcase), and not to my SoftRaid device (/dev/md0)
- I finish the installation et voila.

When I disconnect one of my disks everything boots from the other, so I'm pleased...
Hope this might help anyone else too.

You need to STOP and think real hard about what you are doing and why.

Read up on btrfs for a while first.
BTRFS you can add multiple block devices to a singe filesystem (similar to adding PVs to an LVM)
BTRFS has a concept of subvolumes (similar to LVM logical volumes)
BTRFS has a concept of striped and mirrored storage - similar (not identical) to RAID-1 (and 0). https://btrfs.wiki.kernel.org/index....and_subvolumeshttps://btrfs.wiki.kernel.org/index....or_in_Btrfs.3F
So putting a btrfs on top of LVM on top of RAID1 is certainly possible - but a waste of resources.
I wouldn't imagine anyone using btrfs on top of LVM.
I think only a minority would want to put btrfs on top of RAID0 or RAID1.

So maybe I don't understand your goals in detail - but this sounds like a silly approach.

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