very strange reaction of the md disks

[RW]

On Tue, 03 Jun 2008 11:31:05 +0400
The Ghost <the-ghost at inbox.ru> wrote:

> Hello,
> 
> Maybe I just don't understand something, but anyway, it looks really
> odd.
> 
> I have a machine with 2 Gb RAM with a clean newly-installed
> FREEBSD-7.0-RELEASE. I make two 300-MB mdconfig disks and populate
> them, and when the first one was already full and the second one is
> only half-full, I get a kernel panic "not enough memory". I wonder
> where did 1,5 Gb go?? 

Try using swap-backed md devices instead. With both malloc and swap
devices the data is stored in ram and paged-out to swap as needed, but
it helps with some of the malloc limitations.

I'm using a 2.7GB /tmp directory with 1.6GB of ram and have not had any
problems. I don't actually see any swap usage unless I put a lot of
data on the device, otherwise I can even do a swapoff.