Re: Change Raid Settings

[Jeff Crosby <jlcrosby@xxxxxxxxxxxxxxxx>]

How do I tell whether they're SCSI or SAS?  I think they're SCSI.

Here's the relevant part of WRKDSKSTS

               Size    %
Unit  Type      (M)  Used
   1  4326    35165  22.8
   2  4326    26373  18.1
   3  4326    26373  18.1
   4  4326    26373  18.1
   5  4326    26373  18.1
   6  4326    35165  18.1
   7  4326    35165  18.1
   8  4326    35165  18.1
   9  4326    30769  18.1
  10  4326    30769  18.1
  11  4326    30769  18.1
  12  4326    30769  18.1
  13  4326    30769  18.1
  14  4326    30769  18.1
  15  4326    30769  18.1
  16  4326    30769  18.1

Unit 1 has always had higher usage than the rest.  Due to LIC?

Units 1-8 are 1 RAID set and 9-16 are the other RAID set.

It looks to me like the striping in the first RAID set is over 4 drives
(units 2-5) and the striping is over all 8 drives in the second RAID set.
 Am I reading this right?

FYI:  unit 5 is the one that failed.



On Tue, Sep 24, 2013 at 9:10 AM, <rob@xxxxxxxxx> wrote:

> Are these SAS drives or SCSI drives?  I may be wrong but SCSI drives did
> their raid striping over 2, 4 or 8 drives, depending on how many drives
> were in the raid set when you first fired it up.  For example, if you
> started out with a three drive raid set (YUCK!) you will only have your
> striping over 2 drives, even though your current set may now have 8 drives
> in it.  This is why three drive raid sets suck; the striping is only over
> two drives.  You can often tell how many drives have the raid striping
> when you do a WRKDSKSTS.  The drives with the raid striping will have less
> capacity, because the striping takes away from the capacity.  Much like
> the question a few weeks ago when the poster wondered how he had drives
> with different capacity's in the same raid set.
> So, you're planning on going from a raid stripe spread out over 8 drives
> to a raid stripe spread out only over 4 drives when you drop down from 8
> drives to 7.  This could have performance implications.  Won't be as bad
> as dropping down to a 2 drive raid stripe!  (Pass me the short sword
> master.)
>
> You may have to stop and restart raid to do all this, see?  Don't lose a
> drive during this.
>
> SAS drives spread the raid striping over the number of drives initially in
> there when you start raid.  A three drive raid set should have the stripe
> over three drives and not two.  Now, if you add a drive the striping
> should still stay just over the first drives.  A SAS seven drive raid set
> (with the 8th drive as a hot spare) should have the striping over all
> seven drives.
>
> I hope I am correct.
>
> Rob Berendt
> --
> IBM Certified System Administrator - IBM i 6.1
> Group Dekko
> Dept 1600
> Mail to:  2505 Dekko Drive
>           Garrett, IN 46738
> Ship to:  Dock 108
>           6928N 400E
>           Kendallville, IN 46755
> http://www.dekko.com
>
>
>
>
>
> From:   Jeff Crosby <jlcrosby@xxxxxxxxxxxxxxxx>
> To:     Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>,
> Date:   09/24/2013 08:54 AM
> Subject:        Change Raid Settings
> Sent by:        midrange-l-bounces@xxxxxxxxxxxx
>
>
>
> Yesterday we had a disk failure at 4:27pm, which happens to be 3 minutes
> before we run our entire days business.  Good timing, eh?  We ran
> everything and then replaced the drive and rebuilt the RAID.  I honestly
> don't remember the last time we had a disk failure before this.
>
> Our System i 520 is on i 7.1 and has 16 drives in it.  There are 2 RAID
> sets with 8 drives each.  Disk utilization is less than 19% so we have
> plenty of space.  (We used to have an IXS way back when, which is why
> we're
> way over capacity on disk.)
>
> The service guy (ServIT) thought, since we're on 7.1, it might be possible
> to change each of those 8-drive RAID sets to a 7-drive RAID set with a hot
> spare.  I questioned him because of the age of our hardware and said he
> still thought it was possible.  He's going to look into it today.
>
> Since there are some very smart hardware people on this list, I'm going to
> ask here.  Can that be done?  Can that be done without a reload?
>
>
> Thanks.
>
> --
> Jeff Crosby
> VP Information Systems
> UniPro FoodService/Dilgard
> P.O. Box 13369
> Ft. Wayne, IN 46868-3369
> 260-422-7531
> www.dilgardfoods.com
>
> The opinions expressed are my own and not necessarily the opinion of my
> company.  Unless I say so.
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