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

[Duncan]

Mark Knecht posted on Tue, 30 Mar 2010 13:26:59 -0700 as excerpted:

> 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.

That depends on your BIOS.  My current system (the workstation, now 6+ 
years old but still going strong as it was a $400+ server grade mobo) will 
boot from whatever disk I tell it to, but keeps the same BIOS disk order 
regardless -- unless I physically turn one or more of them off, of 
course.  My previous system would always switch the chosen boot drive to 
be the first one.  (I suppose it could be IDE vs. SATA as well, as the 
switcher was IDE, the stable one is SATA-1.)

So that's something I guess you figure out for yourself.  But it sounds 
like you're already well on your way...

>> 100% waits for long periods...

>> 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.

That's good. =:^)  Tho of course there's an infant mortality period of the 
first few (1-3) months, too, before the statistics settle down.  So just 
because they're new doesn't necessarily mean they're not bad.

FWIW, when I switched to RAID was after having two drives go out at almost 
exactly the year point.  Needless to say I was a bit paranoid.  So when I 
got the new set to setup as RAID, the first thing I did (before I 
partitioned or otherwise put any data of value on them) was run
badblocks -w on all of them.  It took well over a day, actually ~3 days 
IIRC but don't hold me to the three.  Luckily, doing them in parallel 
didn't slow things down any, as it was the physical disk speed that was 
the bottleneck.  But I let the thing finish on all four drives, and none 
of them came up with a single badblock in any of the four patterns.  
Additionally, after writing and reading back the entire drive four times, 
smart still said nothing relocated or anything.  So I was happy.  And the 
drives have served me well, tho they're probably about at the end of their 
five year warranty right about now.

The point being... it /is/ actually possible to verify that they're 
working well before you fdisk/mkfs and load data.  Tho it does take 
awhile... days... on drives of modern size.

>> 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.

You may wish to take a second look at that, for an entirely /different/ 
reason.  If those are the ones I just googled on the WD site, they're 
rated 300K load/unload cycles.  Take a look at your BIOS spin-down 
settings, and use hdparm to get a look at the disk's powersaving and 
spindown settings.  You may wish to set the disks to something more 
reasonable, as with 8 second timeouts, that 300k cycles isn't going to 
last so long...

You may recall a couple years ago when Ubuntu accidentally shipped with 
laptop mode (or something, IDR the details) turned on by default, and 
people were watching their drives wear out before their eyes.  That's 
effectively what you're doing, with an 8-second idle timeout.  Most laptop 
drives (2.5" and 1.8") are designed for it.  Most 3.5" desktop/server 
drives are NOT designed for that tight an idle timeout spec, and in fact, 
may well last longer spinning at idle overnight, as opposed to shutting 
down every day even.

I'd at least look into it, as there's no use wearing the things out 
unnecessarily.  Maybe you'll decide to let them run that way and save the 
power, but you'll know about the available choices then, at least.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman