Re: [gentoo-amd64] Re: RAID1 boot - no bootable media found

[Mark Knecht]

On Tue, Mar 30, 2010 at 11:08 AM, Duncan <1i5t5.duncan@×××.net> wrote:
> Mark Knecht posted on Tue, 30 Mar 2010 06:56:14 -0700 as excerpted:
>
>> 3) I LOVE your idea of managing 3 /boot partitions by hand instead of
>> using RAID. Easy to do, completely testable ahead of time. If I ensure
>> that every disk can boot then no matter what disk goes down the machine
>> still works, at least a little. Not that much work and even if I don't
>> do it for awhile it doesn't matter as I can do repairs without a CD.
>> (well....)
>
> That's one of those things you only tend to realize after running a RAID
> for awhile... and possibly after having grub die, for some reason I don't
> quite understand, on just a kernel update... and realizing that had I
> setup multiple independent /boot and boot-backup partitions instead of a
> single RAID-1 /boot, I'd have had the backups to boot to if I'd have
> needed it.
>
> So call it the voice of experience! =:^)
>
> Meanwhile, glad you figured the problem out.  A boot-flag-requiring-
> BIOS... that'd explain the problem for both the RAID and no-RAID version!

I've set up a duplicate boot partition on sdb and it boots. However
one thing I'm unsure if when I change the hard drive boot does the old
sdb become the new sda because it's what got booted? Or is the order
still as it was? The answer determines what I do in grub.conf as to
which drive I'm trying to use. I can figure this out later by putting
something different on each drive and looking. Might be system/BIOS
dependent.

>
> 100% waits for long periods...  I've seen a number of reasons for this.
> One key to remember is that I/O backups have a way of stopping many other
> things at times.  Among the reasons I've seen:
>

OK, so some new information is another person the RAID list is
experiencing something very similar with different hardware.

As for your ideas:

> 1a) Dying disk.
> 1b) hard to read data sectors.

All new drives, smartctl says no problems reading anything and no
registered error correction has taken place.

>
> 2) DHCP

Not using it, at least not intentionally. Doesn't mean networking
isn't doing something strange.

>
> 3) suspend the disks after a period of inactivity

This could be part of what's going on, but I don't think it's the
whole story. My drives (WD Green 1TB drives) apparently park the heads
after 8 seconds (yes 8 seconds!) of inactivity to save power. Each
time it parks it increments the Load_Cycle_Count SMART parameter. I've
been tracking this on the three drives in the system. The one I'm
currently using is incrementing while the 2 that sit unused until I
get RAID going again are not. Possibly there is something about how
these drives come out of park that creates large delays once in
awhile.

OK, now the only problem with that analysis is the other guy
experiencing this problem doesn't use this drive so that problem
requires that he has something similar happening in his drives.
Additionally I just used one of these drives in my dad's new machine
with a different motherboard and didn't see this problem, or didn't
notice it but I'll go study that and see what his system does.

>
> 4) I/O priority inversion on ext3

Now this one is an interesting idea. Maybe I should try a few
different file systems for no other reason than eliminating the file
system type as the cause. Good input.

Thanks for the ideas!

Cheers,
Mark