Arch Linux

jamespharvey20

Member

Registered: 2015-06-09

Posts: 129

Booting off raid'ed > 2GB drives, btrfs, handling bios boot partition

Setting up an array of (3) 5GB drives using btrfs.  It will soon grow to (6) 5GB drives.  Starting with raid 1, will rebalance once all the drives are installed to either raid5, 6, or 10.

I will be booting off of this, so I believe I need a bios_grub / BIOS boot partition.

How is this usually done?  I'm starting with:

# parted /dev/sda
mklabel gpt
mkpart grub ext3 1M 2M
set 1 bios_grub on
mkpart btrfs btrfs 2M 5001GB

I guess my preference would be that the BIOS boot partition be a raid 1 across all 3 (eventually 6), so there isn't just one drive hosting the boot partition that if it dies preventing booting before re-installing the boot partition to another drive.

mkfs.btrfs won't run on a 1MB partition.  Says the minimal size for each btrfs partition is around 16MB.

Syslinux can't boot off btrfs yet, so that's not an option.  (In this paragraph, using "boot" not in the sense of the bios_boot partition, bot the rest of the boot sequence.)

Would you increase sdX1 to 20MB, make a 20MB on each drive, and make a btrfs raid1?  (The 20MB doesn't matter at all with these sizes.)

Or, would you make a 1MB partition on each, make it ext3, and a mdadm raid1?  (Not even sure a mdadm raid can work for a bios_grub partition...)

Last edited by jamespharvey20 (2015-07-20 22:27:52)

jamespharvey20

Member

Registered: 2015-06-09

Posts: 129

Re: Booting off raid'ed > 2GB drives, btrfs, handling bios boot partition

Now I'm thinking perhaps the way to go is skip mdadm, and:

grub-install /dev/sdc
grub-install /dev/sdb
grub-install /dev/sda

This will copy grub into /boot/grub 3 times, overwriting itself 2 times, but it should install grub into each drive's boot sector, and if order matters (don't think it does) then sda is most recent.

Slithery

Administrator

From: Norfolk, UK

Registered: 2013-12-01

Posts: 5,776

Re: Booting off raid'ed > 2GB drives, btrfs, handling bios boot partition

Grub doesn't need a special partition if you use the full disks as btrfs instead of partitioning them, this is exactly the setup I use.

slithery@blue:~ lsblk
NAME FSTYPE   SIZE MOUNTPOINT LABEL UUID
sda  btrfs  931.5G /mnt/@vol0 vol0  08f0e554-5aa6-46a5-8d5d-5ba4ab168660
sdb  btrfs  931.5G            vol0  08f0e554-5aa6-46a5-8d5d-5ba4ab168660

https://wiki.archlinux.org/index.php/Btrfs#GRUB

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No, it didn't "fix" anything. It just shifted the brokeness one space to the right. - jasonwryan
Closing -- for deletion; Banning -- for muppetry. - jasonwryan

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