usb raid1 pendrive boot
On Friday 07 May 2010 08:22:00 deloptes wrote:
> Jozsi Vadkan wrote:
> > Did anyone managed to boot from RAID1?
> > Lenny gives this error message:
> > "mdadm: no devices found for /dev/md0"
> You'll need a small i.e. 20-30MB partition out of raid to boot from with
> i.e. initrd which loads the md driver and your raid device becomes visible.
* Just for the record, it actually *is* possible to boot off a partition
that's in RAID1, but you might have to use grub. *The reason it works
is because grub can read past the md-raid1 metadata without getting
confused -- since the raid is not running when grub is looking at the
disks, it only sees one of the two, but since they're mirrored, and
since grub doesn't *write* to the partition, everything works.
* I have several production systems that do this.
* It's a bit complicated to set up, but generally, it goes
* - Install a basic system onto one drive, with the correct
* * * size of partition (call this /dev/sda1).
* - Set up an "incomplete" RAID1 array, with one device and
* * * one missing, with the second drive -- this is /dev/md0,
* * * consisting of /dev/sdb1 and an empty slot.
* - Configure /etc/mdadm/mdadm.conf, and re-build your initramfs
* * * so that it has the md modules and knows about the array.
* - Mount /dev/md0 somewhere and copy all the data off /dev/sda1 to it.
* * * It's very important to get the *new* initramfs onto the array.
* - Install grub in the bootloader of the 2nd drive. (The installer
* * * already did this for the first one). This actually isn't
* * * essential, but you may need it if/when /dev/sda fails.
* - Boot on to the incomplete RAID array -- root=/dev/md0.
* - Add /dev/sda1 to the array, and sync.
* Now you have a bootable software raid-1 system.
* I'm not saying this solves the OP's problem, necessarily,
but it's perfectly possible. *I've never tried it with LILO
or grub2, but I would think it would work.
Andrew Reid / email@example.com
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