Re: Huge Data sets, simple queries

[Kevin <kev(at)drule(dot)org>]

Luke Lonergan wrote:
> Jim,
>
> On 1/30/06 12:25 PM, "Jim C. Nasby" <jnasby(at)pervasive(dot)com> wrote:
>
>   
> > Why divide by 2? A good raid controller should be able to send read
> > requests to both drives out of the mirrored set to fully utilize the
> > bandwidth. Of course, that probably won't come into play unless the OS
> > decides that it's going to read-ahead fairly large chunks of the table
> > at a time...
> >     
>
> I've not seen one that does, nor would it work in the general case IMO.  In
> RAID1 writes are duplicated and reads come from one of the copies.  You
> could alternate read service requests to minimize rotational latency, but
> you can't improve bandwidth.
>
> - Luke   
>
>   
For Solaris's software raid, the default settings for raid-1 sets is:  
round-robin read, parallel write.   I assumed this mean't it would give 
similar read performance to raid-0, but I've never benchmarked it.

-Kevin