Re: 20 drives, raid 5 with hot spare, puts two drives in hot spare

[DrFranken <midrange@xxxxxxxxxxxx>]

Either of the two controllers can control the RAID set but only one of 
them 'owns' it at any moment.

Because there are two paths to all SAS disks BOTH controllers have a 
dedicated path to each disk so yes you will see all 20 drives under each 
of the two RAID cards. In fact one of the failures I have seen is where 
a drive loses a path and thus only one RAID card could communicate with 
it. In this case a drive replacement is required as you would expect. 
You can see this in work with disk units, display path status.

As for the hot spares I'm not sure why with only one RAID set it 
allocated two in your case. I would have expected it to create two RAID 
sets of 9 each with a hot spare. In theory this would have provided 
better throughput as each controller now is handling 9 drives while the 
current configuration has one controller cooling it's heels while the 
other does all the work.

Of course the degree of additional performance may be insignificant and 
without testing, I suppose it's more of a hunch than a fact.

Are your RAID controllers set for Performance, Capacity, or Balanced?

        - Larry "DrFranken" Bolhuis

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

On 4/28/2014 11:16 AM, rob@xxxxxxxxx wrote:
> So, this raid set is owned by two controllers?  And each of those
> controllers has a hot spare?
>
> WRKHDWRSC *STG
> Resource        Type-model  Status                Text
> CMB02            xxxx-001   Operational           Storage Controller
>    DC02           xxxx-001   Operational           Storage Controller
> ...
> CMB11            xxxx-001   Operational           Storage Controller
>    DC05           xxxx-001   Operational           Storage Controller
>
> and using "9=Work with resource"
> shows two "Device Services" and all 20 drives for each of these two
> Storage Controllers.  Option 7 shows one storage controller in one slot
> and one in another.
>
> So, if I would have set it up with two raid sets I would still only use
> two hot spares.  One for each controller.
>
>
> Rob Berendt