Re: performance on new linux box

On Thu, Jul 8, 2010 at 12:46 PM, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov
> wrote:

> Ryan Wexler <ryan(at)iridiumsuite(dot)com> wrote:
>
> > One thing I don't understand is why BBU will result in a huge
> > performance gain. I thought BBU was all about power failures?
>
> Well, it makes it safe for the controller to consider the write
> complete as soon as it hits the RAM cache, rather than waiting for
> persistence to the disk itself. It can then schedule the writes in
> a manner which is efficient based on the physical medium.
>
> Something like this was probably happening on your non-server
> machines, but without BBU it was not actually safe. Server class
> machines tend to be more conservative about not losing your data,
> but without a RAID controller with BBU cache, that slows writes down
> to the speed of the rotating disks.
>
> -Kevin
>
Thanks for the explanations that makes things clearer. It still amazes me
that it would account for a 5x change in IO.