Re: RAID1 and load-balancing during read

[Dimitrios Apostolou <jimis@gmx.net>]

On Monday 10 September 2007 22:35:30 Iustin Pop wrote:
> On Mon, Sep 10, 2007 at 10:29:30PM +0300, Dimitrios Apostolou wrote:
> > Hello list,
> >
> > I just created a RAID1 array consisting of two disks. After experiments
> > with processes *reading* from the device (badblocks, dd) and the iostat
> > program, I can see that only one disk is being utilised for reading. To
> > be exact, every time I execute the command one of the two disks is being
> > randomly used, but the other one has absolutely no activity.
> >
> > My question is: why isn't load balancing happening? Is there an option
> > I'm missing? Until now I though it was the default for all RAID1
> > implementations.
>
> Did you read the archives of this list? This question has been answered,
> like, 4 times already in the last months.
>
> And yes, the driver does do load balancing. Just not as RAID0 does,
> since it's not RAID0.

Of course I did a quick search in the archives but couldn't find anything. 
I'll search better, thanks anyway. Moreover, I think I found the answer in 
the code after posting. There is a comment somewhere in read_balance() 
saying "Don't change to another disk for sequential reads". I have to study 
it a bit to figure out *why* you chose that way. 


Thanks, 
Dimitris