John Robinson wrote:
Doesn't need to understand RAID, just be willing to try the next item in the
boot list on failure. My experience has been that almost every BIOS will try the
2nd item if the 1st fails totally (ie. drive isn't there). A _good_ BIOS will
try the next item on sector error in the MBR. After that the BIOS needs to
understand a lot more to do anything smart after the MBR runs.
On 20/04/2012 17:50, Mark Knecht wrote:
On Fri, Apr 20, 2012 at 9:31 AM, John Robinson
On small machines (3-6 drives) I will regularly have a RAID-1 /boot, RAID-10
swap and RAID-5 or 6 everything else, done with partitions. I do use LVM too
though - that "everything else" will be LVM over the big RAID.
Thanks for the info John. Can you tell me what are the requirements
for the RAID-1 /boot? grub2? initrd? BIOS-based RAID? Something else?
I'm still just mirroring my boot drives - booting from sda1 but
copying everything to /sdb1, sdc1, etc. I think I'd like to go full
RAID on /boot if the requirements are too high.
Pretty much any modern distro's installer will do the right thing with whatever
boot loader it uses. Also, there are so many boot methods - BIOS/MBR, GPT, UEFI
- that in one short email it's tricky to give advice in one short email. It's
all out there via Google.
But no, you can do a RAID-1 /boot with LILO or grub, and without BIOS RAID. The
BIOS will boot off the first available hard drive and doesn't understand md
RAID. grub doesn't understand md RAID either. You have to make your md RAID-1
/boot with metadata 1.0 (or 0.90) because they have the data at the beginning so
when you create a filesystem on the array, each individual component (partition)
looks like it has a filesystem on it. You install grub (or LILO) onto the MBR
(or GPT boot partition, which isn't the same as your /boot partition), pointing
to the partition (not the md array).
grub2 does understand md RAID, but has to be loaded by the BIOS, so there are
Without either hardware or BIOS RAID, you can still end up being unable to boot,
e.g. the BIOS will try to boot from the first hard drive present, but if it has
bad sectors in the MBR or /boot partition, booting may fail even though there's
a perfectly good mirror on the second drive, because the BIOS doesn't understand
RAID. This has happened to me :-(
I have put MBR and boot partition on a USB thumb drive because the failure rate
of a R/O flash is lower than rotating devices (in my experience). Use ext2 for
boot, no journal so the drive works really read-only. Hopefully grub2 mounts the
Bill Davidsen <davidsen@xxxxxxx>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
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