[mdlug] "Device busy" errors and RAID setup issues

[Michael Mikowski]

----- Original Message ----
From: David McMillan <skyefire at skyefire.org>
To: MDLUG's Main discussion list <mdlug at mdlug.org>
Sent: Mon, November 23, 2009 7:27:39 AM
Subject: Re: [mdlug] "Device busy" errors and RAID setup issues

[...] It really is starting to smell like a mobo SATA issue. [...]

Yes, it really is.

Maybe this was covered here before, but did you turn OFF raid in the BIOS?  Lots of motherboards come with "FAKE RAID" controllers these days (kinda like WinModems; all the real work is in software).  If it is ON this is bad ju-ju for software RAID.

You might be trying to use the FAKE RAID solution on Linux, although it doesn't sound like.  However, if you have it on in your BIOS, it is possible your distro is doing some magic behind the scenes to use FAKE RAID instead of normal software RAID. 

If you are, you probably want to abandon that effort - from all the research I did on the subject, its more complex, and software RAID beats its performance in most cases anyway.

Bty, on 'buntu, RAID status is stored in /etc/mdadm/mdadm.conf.  Here is my config (all 1 lines of it):

ARRAY /dev/md0 level=raid1 num-devices=2 UUID=89bd7692:13639217:8123ad1b:62b087f3

So my advice, in summary, is:
* Turn off any "RAID support" in your BIOS, if enabled
* Use software RAID only; do not try to use FAKE RAID
* Look to /etc/mdadm/mdadm.conf to store your array settings

Hope that helps.

Cheers, Mike


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