ECC status in FreeBSD

[Charles Swiger]

On Dec 20, 2004, at 3:55 PM, Brett Glass wrote:
> I'm getting ready to build some (hopefully) high reliability servers  
> with
> ECC memory. I'd like to put FreeBSD on them. What facilities (if any)  
> does
> FreeBSD have for:
>
> 1) Reporting the status of ECC memory (errors corrected, errors  
> uncorrected, etc.)?
> 2) Responding to uncorrectable errors?

A quick check of the archives suggests a FreeBSD version of a kernel  
module which pays attention to the ECC status of various chipsets is  
available from:

http://docs.freebsd.org/cgi/getmsg.cgi?fetch=113348+0+archive/2001/ 
freebsd-hackers/20010318.freebsd-hackers

...based on the work for Linux at:

http://www.anime.net/~goemon/linux-ecc/

> 3) Mapping out portions of memory that produce repeated errors?

You can set an option in the loader to limit the physical memory  
available to FreeBSD, which could serve the purpose.

However, your RAM isn't a hard drive, so the ad-sector remapping used  
by hard drives is not fully applicable.  Your machine is expected not  
to have any part of memory fail reproducably, but if you do, it's time  
to use the warranty and replace the entire chip.

> It seems to me that, for an operating system that prides itself on  
> server
> stability and performance, such features are a must.

ECC is a fine idea, but the motherboard chipset pretty much does  
everything that is required (except for the reporting/syslogging), so  
the kernel doesn't need to be specially involved for the system to  
benefit from ECC protection.

-- 
-Chuck