GPT + RAID + boot
My goal here is to be able to have a bootable, running system in the
event of a disk failure. I've been running two disks in a RAID-1
configuration, with grub installed on both disks, for some time. My
/etc/mdadm/mdadm.conf is essentially empty, as mdadm has been
successfully finding my RAID partitions and assembling my arrays at boot
time without it.
I've gotten a new 3TB disk (to replacing an old, failing disk), so I'm
setting up my first GPT partition table.
On my old (MBR) disk, parted shows my first partition as
1 32.3kB 1500GB 1500GB primary boot, raid
and I'm able to boot successfully.
On my new (GPT) disk, I am only able to install grub if I've set the
bios_grub flag (note that this flag doesn't appear in the man page,
though it does appear in the documentaiton at
http://www.gnu.org/software/parted/manual/parted.html#set) on my
partition. If I set the boot or legacy_boot flags, I get
snowball:518$ sudo grub-install /dev/sdb
/usr/sbin/grub-setup: warn: This GPT partition label has no BIOS Boot Partition; embedding won't be possible!.
/usr/sbin/grub-setup: error: embedding is not possible, but this is required for cross-disk install.
Unfortunately, I don't seem to be able to set both the bios_grub and the
raid flags at the same time. If I set the bios_grub flag, printing the
partition table shows no raid flag; if I set the raid flag, printing the
partition table shows no bios_grub flag.
Booting with the bios_grub flag set, my raid array isn't assembled
properly: the partition with bios_grub set isn't added into the array
(fortunately, my other disk is good!).
So: how can I go about setting up my new disk so I will have a two-disk
RAID array if both disks are good, and be able to boot with a degraded
array in the event of either disk failing?
--
"Erwin, have you seen the cat?" -- Mrs. Shroedinger
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