Re: GPT + RAID + boot

2014-01-15 Thread Joe Pfeiffer
Sven Hartge s...@svenhartge.de writes:
PaulNM deb...@paulscrap.com writes:

snip

Thank you both for your help -- your suggestions were exactly what I
needed (I delayed responding until I was confident I had everything
working).

I'm puzzled as to why parted refers to these partition types as
flags -- seeing that when using the program, and when reading the
documentation, coupled with the fact that bios_grub doesn't turn up in
the man page (but only in info), and that disks using MBR actually can
have a boot flag on a partition, certainly helped send me off in the
wrong direction!

But again, thank you both for helping me navigate through this one.


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Re: GPT + RAID + boot

2014-01-08 Thread Sven Hartge
Joe Pfeiffer pfeif...@cs.nmsu.edu wrote:

 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.

Attention!

Don't EVER set the bios_grub flag on ANY partition not specially added
to be a BIOS Boot Partition. If you add this flag to your main data
partition, installing GRUB _WILL_ destroy the data on this partition by
overwriting it.

The BIOS Boot Partition is a replacement for the empty sectors 1 to 62
GRUB uses with an MBR-based disk layout to embed its stage 1.5. Those
sectors are used with the GPT and thus you need a specially created
place to put the initial stages of GRUB.

Solution: Create a small (1MiB is enough) separate partition on _each_
of your disks and then continue to install GRUB via grub-install
/dev/sdX as you would do with a MBR-based disk.

(To be safe, be sure to create this little partition below 2TiB.)

S°

-- 
Sigmentation fault. Core dumped.


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Re: GPT + RAID + boot

2014-01-07 Thread PaulNM
On 01/07/2014 03:20 PM, Joe Pfeiffer wrote:

snip

 
 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?
 

Well, bios_grub and raid aren't flags. They're partition types.

The gpt layout doesn't have as much spare room in it as the older mbr.
Creating a small bios_grub partition gives some space for grub to
install parts of itself.

You need to create a small (recommend 1MB) partition for bios_grub, then
the rest of the drive can be a linux raid partition.

- PaulNM


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