Re: Quick Question on Raid5 w/Hot Spare

[DrFranken <midrange@xxxxxxxxxxxx>]

Yep this is a known limitation of SCSI disks. The LS disk unit needs to 
be in one of the first three slots on SCSI controllers (technically 
first three addresses.) With SAS this restriction is lifted so the 
problem goes away.

*IF* you are still on SCSI disk you may want TWO hot spares for the Load 
Source (slots 2 and 3). That way you can keep host spare protection and 
means you can wait for a maintenance window to move drives around.

Also note that most SCSI disks are getting older so failure rates are 
beginning to climb.

        - Larry "DrFranken" Bolhuis

www.frankeni.com
www.iDevCloud.com
www.iInTheCloud.com

On 4/8/2013 12:15 PM, Jerry Draper wrote:

> With older controllers you can run into this situation:
>
> We had one hot spare and to protect the load source drive it has to be
> in a load source capable position.
>
> We lost a drive (not load source) and the hot spare activated taking the
> place of the dead drive.
>
> Now we were in a tricky position.
>
> Just replacing the dead drive meant that our load source drive would not
> be protected by the hot spare system.
>
> We had to plan for a machine power down to move the drives around so we
> could end up with our hot spare in a load source capable position.
>
> Jerry
>
>
>
> On 4/8/2013 9:08 AM, DrFranken wrote:
> > Per controller.  With redundant cards such as on SAS each card wants to
> > have one.
> >            - Larry "DrFranken" Bolhuis
> >
> > www.frankeni.com
> > www.iDevCloud.com
> > www.iInTheCloud.com
> >
> > On 4/8/2013 11:53 AM, Kirk Goins wrote:
> >
> > > Is the Hot Spare per controller or per Raid5 set?
> > >
> > > Thanks