Can not dump on raid dev?

[Andrew Kinney]

On 29 Sep 2003, at 15:35, Kang Liu wrote:

> Hi,
> 	I'm trying to save a crashdump into /var/crash but it fails.
> Here is my config files:
> # dmesg | grep amr
> amr0: <LSILogic MegaRAID> mem 0xf0000000-0xf7ffffff irq 3 at device 0.0 on pci3
> amr0: <LSILogic PERC 3/DC> Firmware 1.92, BIOS 3.31, 128MB RAM
> amrd0: <LSILogic MegaRAID logical drive> on amr0

<snip>

> when the system crashes, it doesn't save any crashdump. 
> I've tried the same config on a machine with IDE disk, the crashdump can be saved.
> Do I miss something, or the crashdump can not be saved on a raid device? 
> 

We had the same trouble with the mlx driver under 4.5, 4.7, and 
4.8.  The driver doesn't support crash dumps.  I even tried making a 
ccd device since the driver code for ccd appears to support crash 
dumps.  Didn't have any luck with that either.  Ended up taking an 
old 4GB IDE hard drive and setting it up as a dedicated crash 
dump device.  

Just be sure you don't mount the swap partition you create on it 
because you don't want to compromise the benefits of having a 
RAID if you're using it for redundancy.  The only other trick with 
that is that you have to have a BIOS that will allow you to define 
SCSI/RAID as your primary boot device.  Some automatically 
assume you want to use IDE for boot if you have and IDE hard drive 
installed.  If you're using RAID, you're probably also using a decent 
server board that includes the necessary boot options.

If memory serves correctly, from what I read in the code, the only 
block device drivers that support crash dumps are IDE and some 
Adaptec SCSI cards.  Don't know for sure about those Adaptec 
SCSI cards since we're not using one and you can't always trust 
what you see in the code about dumps as evidenced by the ccd 
driver.  I believe it has something to do with it being necessary to 
use BIOS routines to write to the device since by the time you're 
doing a crash dump all your high level drivers are not useable 
anyway.

Hope that helps.

Sincerely,
Andrew Kinney
President and
Chief Technology Officer
Advantagecom Networks, Inc.
http://www.advantagecom.net