experimantal question about md's

[RW]

On Fri, 26 Sep 2008 20:15:43 +0200
"Michael Schuh" <michael.schuh at gmail.com> wrote:


> Let us say i have a Machine with 8 CPUs and a lot of RAM.
> An i need a very high perfomance Storage for holding data.
> 
> My idea was to setup a raid1(0) with virtual disk images.
> Created with mdconfig.
> 
> My idea was to create minimum 2 md-diskimages,
> these are located
> fisrt one on the harddisk as type vnode
> second one as exact copy totally in the memory as type malloc
> 
> For now the man-page mentoid me to not to do so, while large disks in
> RAM cause panics, and i know panics come surely
> 
> Is the above scenario possible without panics?

You could use swap-backed devices. They are very similar, in both cases
you are writing into ram backed by swap.

I doubt it will work, I think raid works at the speed of the slower
device. You need to be careful how you benchmark it. Your raid array
will have the unfair advantage of starting with preloaded data.