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Larry,

I think I found why 2 hot spare units where used as opposed to 1.
There are two ways to include the hot spare disk units in your system:

I used the option 5. Start device parity protection - RAID 5 with hot spare, which the system decided to use 2 hot spare units.

Instead, I should have:

After adding units to the ASP, I should have left one unit non-configured, then
Option 9. Start Hot Spare
Select this option to allow a hot spare disk unit to be
created. If a Storage IOA is selected and sufficient
resources are available, a single hot spare disk unit
is created under that IOA. If a disk unit is selected,
that disk will become the hot spare disk unit.
The disk unit remains reserved as a hot spare disk unit,
until a failure occurs in the parity set and the hot
spare disk unit replaces the failed unit.

Option 1. You can configure the hot spare disk unit when you initially start device parity protection. Starting device parity protection with hot spare protection explains how to include hot spare disk units when starting device parity protection. When selecting this option," the system automatically determines if one or two hot spares should be created" and which available disk units are selected based on the total number and capacity of disk units attached to the IOA.
Note: When you start device parity protection with hot spare disk units, the new hot spare disk units are not committed to any particular parity set. The hot spare disk unit protects the first failed disk unit that has parity protection, is the appropriate capacity for the hot spare, and is under the same IOA as the hot spare.

Option 2. You can create a hot spare disk unit from non-configured disk units on your system. Starting hot spare protection explains how to include hot spare disk units to your system. When selecting this option, you should determine if one or two hot spares are desired and which available units will become hot spares based on the total number of disk units attached to the IOA and their capacity.

To resolve this,
1) I could 10. Stop hot spare, 2. Include unit in device parity protection, 2. Add units to ASPs.
But this would result with non-even parity stripping.

Or

2) As a second option, 10. Stop hot spare , move all data off these drives, IPL to DST, stop parity, IPL, from SST 3. Start device parity protection - RAID 5, 2. Add units to ASPs, STRASPBAL
This would require much more planning, more down time, (stop parity) not sure how long this will be.
Parity stripping would be even.

Paul

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of DrFranken
Sent: Sunday, March 15, 2015 3:15 PM
To: Midrange Systems Technical Discussion
Subject: Re: 177 SSD to 775 SSD Disk Swap, including load source

Comments in line....

- Larry "DrFranken" Bolhuis

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

On 3/15/2015 1:56 PM, Steinmetz, Paul wrote:
<snip>

1) When starting RAID-5 with hot spare, I lost 2 units to hot spare, originally I was informed only 1 would be needed, not sure why?
Documentation states you only need 1 hot spare per IOA.
Not sure if I can correct this, possibly remove the 2nd hot spare.

You said it, "Per IOA" and since you have two 5913s... :-)

Yes you could remove the second one but I would recommend against doing that.


2) When adding disks, if empty disk slots available,, use 8. Device Concurrent Maintenance and avoid IPL.
IPL marks drives as "dirty" and forces an initialize during prep. 140 minutes for a single 775 SSD.
Last week I had to cancel option 9, disk to disk copy of load source because of this added prep time.

Excellent point. So long as the RAID card knows that it has written the drive full of zeros (initialized it) you save that time so doing that in
advance of copy or start RAID takes that time off the critical path.

3) "Prep" or "Initialize" times.

According to IBM, when Option 9, copy disk unit data, requests the destination disk.
IBM sends a command to the disk.
If it comes back as a "clean" disk, then initialize is NOT done.
If it comes back as a "dirty" disk, then IBM issues the command to format the drive.
Each drive manufacture may do formatting differently.
Currently, there is no known method to determine if a drive is "clean" or "dirty"

This also applies when "Adding to ASP"

So it's not IBM's code, but the various disk manufactures format procedures and if a disk is "clean" or "dirty" that determine the time needed for "load source disk to disk copy" and/or "add to asp".

Hmmm. That's interesting, seems like IBM could tell them how to initialize prior to shipping!

My other 5 drives must have been "clean" only 1 minute to "Add to ASP"
When drives where smaller, 4, 8, 17, 35 etc, these times were much smaller.

IBM is working to reduce these "Prep" times in future release as these times keep increasing as drives get larger.

4) When moving the load source, IPL to DST,
A) Add new drives concurrent.
B) Start RAID-5 with hot spare, 1 minute
C) Load source move - option 9, disk to disk copy.
D) Load source "prep" only 1 minute, "clean" drive and new parity set.
E) Load source copy from old 177 SSD to new 775 SSD, 40 minutes.
F) Delay adding other drives to ASP, do after IPL using SST, not DST. 3 to 4 hours.

5) After all new disks are added
STRASPBAL TYPE(*CAPACITY) TIMLMT(*NOMAX) PRIORITY(*MEDIUM)

Thank You
_____
Paul Steinmetz
IBM i Systems Administrator

Pencor Services, Inc.
462 Delaware Ave
Palmerton Pa 18071

610-826-9117 work
610-826-9188 fax
610-349-0913 cell
610-377-6012 home

psteinmetz@xxxxxxxxxx<mailto:psteinmetz@xxxxxxxxxx>
http://www.pencor.com/







Thank You
_____
Paul Steinmetz
IBM i Systems Administrator

Pencor Services, Inc.
462 Delaware Ave
Palmerton Pa 18071

610-826-9117 work
610-826-9188 fax
610-349-0913 cell
610-377-6012 home

psteinmetz@xxxxxxxxxx<mailto:psteinmetz@xxxxxxxxxx>
http://www.pencor.com/

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