Re: Reducing number of disks with RAID5 active.

[DrFranken <midrange@xxxxxxxxxxxx>]

Roberto,

	With SCSI disks there will be stripes created depending on the number 
of disks in the set to start.

Total	07x	070
Disks	Disks	Disks
  3	  2	  1
  4	  4	  0
  5	  4	  1
  6	  4	  2
  7	  4	  3
  8	  8	  0
  9	  8	  1
 10	  8	  2
	etc.

So if you always started with 4 or 8 disks you won't see any 070's until 
you add more but if you start with an odd number you'll always see at 
least one 070.

With SAS disks you will only see 070s when disks are added to an 
existing RAID set.

        - Larry "DrFranken" Bolhuis

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

On 6/4/2013 10:43 PM, Roberto José Etcheverry Romero wrote:

> Doctor, i've never seen a model 070 disk, i always see 072 or 074 disks, i
> think the only way to get a 070 disk is to add a disk to an already created
> raidset, so it doesnt redistribute parity like when starting from scratch,
> I'll check tomorrow (have to continue rebuilding that 520 with the busted
> loadsource), but in any case, extremely good to know that 070 model disks
> could be drained  may be a reason to invest the time in making a raidset
> and then adding the last disk...
>
> Best Regards,
>
>
>
> On Tue, Jun 4, 2013 at 10:54 PM, DrFranken <midrange@xxxxxxxxxxxx> wrote:
>
> > Maybe.
> >
> > At least one of the drives will be a model -070. This indicates that the
> > drive does not contain any parity data. So that's the one you want to
> > drain. This much will work for sure.
> >
> > Now you need to select this drive and remove from parity protection.
> > Theoretically this will work because the drive doesn't contain any data
> > so only the other 7 drives need to be updated.
> >
> > *HOWEVER* do not be surprised if the system says NO to this because with
> > a drive down the RAID set could be somehow 'locked'.
> >
> > Assuming that completes, then use concurrent maintenance and remove it
> > from the system. Next use concurrent maintenance to remove the 'dead'
> > drive and put the removed one in it's place.
> >
> > Now rebuild the data. And you win.
> >
> >           - Larry "DrFranken" Bolhuis
> >
> > www.frankeni.com
> > www.iDevCloud.com
> > www.iInTheCloud.com
> >
> > On 6/4/2013 11:14 AM, Roger Vicker, CCP wrote:
> > > I am trying to salvage an old system on V5R4 using Raid5 on nine disk
> > > drives.
> > >
> > > Disk Unit 1 has failed. I want to remove Disk Unit 9 from the pool
> > > (moving data off) and remove it from the Raid Set. Then use it to
> > > replace the failed Unit 1.
> > >
> > > I have only been able to find online documentation on doing this with
> > > iSeries Navigator. However, the copy I have does not show anything under
> > > <Configuration><Hardware><Disk Units>. Can this be done with just SST
> > > (and maybe DST) and if so would someone mind posting a link.
> > >
> > > Thanks
> > >
> > > Roger Vicker, CCP
> > --
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