Re: questions about io scheduler

[Bill Davidsen]

Mike Fedyk wrote:
> Timothy Miller wrote:
>
> > Mike Fedyk wrote:
> >
> > > Nick Piggin wrote:
> > >
> > > > Kyle Wong wrote:
> > > >
> > > > > 2. Does io scheduler works with md RAID? Correct me if I'm wrong,
> > > > > io-schedular <-->  md driver <--> harddisks.
> > > >
> > > > It goes md driver -> io schedulers -> hard disks.
> > >
> > >
> > >
> > >
> > > There is an IO scheduler per disk.
> > >
> > > So MD submits the data to each disk through the IO scheduler.
> > >
> > > This allows you to have the heads on each disk in the array at 
> > > different locations, and helps keep response times lower for seeky 
> > > loads.
> >
> >
> >
> > Say you've got a RAID1.  In this case, MD could send the read request 
> > to either device.  How does it decide which one to use?
>
>
> The one with the drive head closest to the data.

Or hopefully the one not in use if one is busy...

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