[ Re: Mirroring on i5/OS]

Ah, in a perfect world, all you said is true.
In this case the BCS has only one SAS Connectivity module so all the drives in the chassis are only on the "left" . ( Hmmmm that explains why the lights flash when I say "Obama!" ) Anyway, in this small BCS I only have one 3267. IF I had two, when I had configured the Chassis using the AMM I could have chosen the pairs to be from both sides and, yes, that would have been a bit more failsafe.

Since this is a development machine and we are a small shop, I am most concerned about data loss rather than uptime. Mirroring, even with one controller, will be better than no protection. The good news is that the HW is relatively cheap and is available on the used market so I may stoke up the "right" side when the economy improves or when I am forced to because of space constraints.

Always good to get a second opinion from the "Doctor".

Thanks,

Pete

Larry Bolhuis wrote:

Pete,

Sorry to chime in late here but.... now the bad news. Because the disks are in the BCS chassis (and you mentioned the Virtual disk message) i5/OS hasn't a clue where those disks really are. Heck they might not even be real disks! (You could have virtualized them through VIOS) So what you don't know unless you paid close attention is whether the disks are 'left side, right side'. That is for maximum protection you should have the disks on the left side of the chassis mirrored to the disks on the right side of the chassis. Otherwise if the disk cage fails or loses power your i5/OS goes down even though it didn't have to.

Now if you have only the left cage then your protection is as good as it gets. With four drives I suspect this may be the case.

As you discovered the initial Mirroring setup for the system ASP MUST be done from DST and it mirrors the drives currently in the ASP. It does that by first figuring out the best mirrored pairs (Loop level if possible, if not then Bus level, if not then IOA level, if not then disk level, if not then can't mirror) Once the Pairs are determined then half of them are drained to zero thus doubling the content of the remainder. Then the ASP size is reduced by 1/2 and finally all the disks which contain data are copied to those that don't and shazaam. (OK a slow shazaam) you have mirrored pairs.

In the case of the BCS you must assure that the first two disks in the system are the only two and that one of them is on the left side and the other on the right. Then start mirroring. Once that is done you can use iNav to add disks in pairs (one left, one right) until all disks are added. You cannot add more than two at a time or they may mirror left-left and right-right which reduces the protection level.

Hope that helps!

- Larry

Larry Bolhuis IBM Certified Advanced Technical Expert - System i Solutions
Vice President IBM Certified Systems Expert:
Arbor Solutions, Inc. System i Technical Design and Implementation V5R4
1345 Monroe NW Suite 259 eServer i5 iSeries LPAR Technical Solutions, V5R3 Grand Rapids, MI 49505 IBM Certified Specialist
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(616) 451-2500 System i IT Simplification: Linux Technical V5R4
(616) 451-2571 - Fax iSeries System Administrator for OS/400 V5R3
(616) 260-4746 - Cell If you can read this, thank a teacher....and since it's in English, thank a soldier.




*Pete Helgren <Pete@xxxxxxxxxx>*
Sent by: midrange-l-bounces@xxxxxxxxxxxx

11/13/2008 11:04 AM
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Re: Mirroring on i5/OS









Wayne,

Both you and Pete were correct on this (I think). I started out with
the two drives, unprotected, and wanted to mirror them to the two
non-configured drives I had. When I couldn't do that with iNav, I just
figured it was a "feature" in iNav. I think it was, instead, an issue
with one of the two drives being the load source and needing to be
individually mirrored first. I was trying to mirror BOTH in iNav. What
I ended up doing was to mirror the drives in DST. However, even though
I *thought* was was mirroring the pair, even in DST I ended up with my
two configured but unprotected disks being mirrored to each other, going
from 254GB to 127GB in capacity. I followed what I thought was the
correct steps, confirmed by Lukas, to take the option to select the two
configured, unprotected drives and start mirroring and it would
"automagically" find the non-configured pair and use them to mirror. Not so. The two I selected were mirrored to each other as the load source.

When that was done I saw what had really happened in iNav. So I took
the option in iNav to add disks to the mirror protected "disk pool" and
it would only allow me to add the unconfigured *pair* to the pool, which
makes sense. When I took that option, I eventually ended up with two
mirrored pairs in the pool.

So, you were correct, I just needed to first mirror the load source and
THEN use the unconfigured pair to add to that mirrored pool. I probably
just misunderstood your instructions. Pete was correct in that it could
be done from DST pretty clearly (it WAS a bit clearer in DST).

So again, thanks. 4 hours of machine time got the job done and all is
well and protected.

Pete


Wayne McAlpine wrote:
> Your two disks are each more than half full, with one being the load
> source, so they can't be mirrored. When you add two more disks, you
> should be able to have two mirrored pairs.
>
> Pete Helgren wrote:
> >> I am still not understanding I guess.
>>
>> I have (had) two disks in the pool that had no mirrored protection. I
>> had two other non-configured units that I could use for mirroring (I
>> assumed). What I need are the steps for creating the mirror. When I
>> first went into iNav, and went to "Disk Units" under Hardware, there was
>> one pool: "Disk Pool 1". I had two disks in that pool. Taking the
>> option for Mirroring --> Start Mirroring I got a message saying "There
>> are no eligible disk pools for the action "Start Mirroring" "
>> So the question is: With two disks allocated to Disk Pool 1 and given
>> that there aren't any disk pools eligible for mirroring, how do I create
>> a disk pool that IS eligible?
>> The bummer is, while I was waiting for a post back, I added the two
>> non-configured units to the asp and now I can't remove them. I think
>> I'll go to DST and straighten this out. The iNav route isn't getting me
>> there.
>>
>> Pete
>>
>>
>> Wayne McAlpine wrote:
>> >>> If you add a pair of disks to the mirrored storage pool, they will
>>> automatically be mirrored. It has its own algorithms to figure out
>>> the most effective mirroring configuration, i.e., bus level,
>>> controller level, or disk level.
>>>
>>> Pete Helgren wrote:
>>> >>> >>>> What is throwing me is whether I need to add the non-configured disks
>>>> to the pool first and then implement the mirroring or start mirroring
>>>> and indicate that I want the non-configured units to be the mirrors. >>>> Seems like a chicken or egg thing: If I add the non-configured units
>>>> to the asp, they won't be available to be the mirrored pair (I think).
>>>>
>>>> With raid 5 you just add the units to the asp and tell it to start
>>>> RAID protection and it all seems to work. With mirroring, I not sure
>>>> how to tell the configuration tool that the non-configured units are
>>>> the ones I want to be mirrors. Even in iSeries Navigator, it isn't
>>>> clear. I guess I'll try adding the non-configured units and then see
>>>> if I can start mirroring after they are added to the pool.
>>>>
>>>> Otherwise, I'll try Pete's approach and see what my options are at
>>>> IPL time.
>>>>
>>>> Thanks
>>>>
>>>> Pete
>>>>
>>>>
>>>> Wayne McAlpine wrote:
>>>> >>>> >>>>> I believe you can also do it from iseries Navigator. Click on
>>>>> Disks-->Disk Pools-->right click on the pool to mirror and take the
>>>>> option to start mirroring.
>>>>>
>>>>> Pete Massiello wrote:
>>>>> >>>>> >>>>> >>>>>> Pete,
>>>>>>
>>>>>> Try booting up in Manual mode and go into DST and WORK WITH DISK
>>>>>> Configuration. From there you will see what you need.
>>>>>>
>>>>>> Pete
>>>>>>
>>>>>> Pete Massiello
>>>>>> iTech Solutions
>>>>>> http://www.itechsol.com
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: midrange-l-bounces@xxxxxxxxxxxx
>>>>>> [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Pete Helgren
>>>>>> Sent: Wednesday, November 12, 2008 1:52 PM
>>>>>> To: Midrange Systems Technical Discussion
>>>>>> Subject: Mirroring on i5/OS
>>>>>>
>>>>>> I thought this would be easy but I must be a little slow this week...
>>>>>>
>>>>>> I have my JS12 configured with 4 drives allocated to i5/OS (More
>>>>>> accurately I have VIOS allocating 4 drives to the JS12 from the 6
>>>>>> available in the BCS). Two of which I have configured as part of >>>>>> ASP1. All is well. However, I'd like to get some protection on
>>>>>> these drives and my understanding was that mirroring is my only
>>>>>> option. So, how to I achieve that ? Disk hardware status shows this:
>>>>>>
>>>>>> Serial Resource Hardware ASP
>>>>>> Unit Number Type Model Name Status 1 1 >>>>>> YWEB5KZWKZRX 6B22 050 DD004 Operational
>>>>>> 1 2 Y9EJAR7L8YMZ 6B22 050 DD003 Operational
>>>>>> Y384SV9UX3VE 6B22 050 DD001 Operational
>>>>>> YJA2X8PBPAUR 6B22 050 DD002 Operational
>>>>>>
>>>>>> So, as far as I understand it, the two drives that are unallocated
>>>>>> could be used to mirror the other drives but I don't see any option
>>>>>> in SST to use these drives in a mirrored arrangement. Work with
>>>>>> Device Parity protection show the following menu:
>>>>>>
>>>>>> 1. Display disk configuration 2. Include unit in device parity
>>>>>> protection 3. Start device parity protection - RAID
>>>>>> 5 4. Start device parity protection - RAID
>>>>>> 6 5. Start device parity protection - RAID 5 with hot
>>>>>> spare
>>>>>> 6. Start device parity protection - RAID 6 with hot spare
>>>>>> 7. Select parity optimization No mention
>>>>>> of mirroring.....
>>>>>>
>>>>>> So, how do I mirror these things? I get plenty of hits on mirroring
>>>>>> "Concepts" in the infocenter but precious little about
>>>>>> implementation. Running IBM i 6.1 on a JS12.
>>>>>>
>>>>>> Pete
>>>>>>
>>>>>>
>>>>>>
>>>>>> >>>>>> --
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