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Migrate to NVME mirrored by IBM i

  • 1.  Migrate to NVME mirrored by IBM i

    Posted Mon June 05, 2023 11:46 AM

    Hello,

    We are planning to migrate a whole Power 9 system with eight (8) ESNJ 283GB 15K RPM SFF-3 disks on RAID 5 with hot spare, to a new Power 10 with only two (2) EKF4  Enterprise 1.6 TB SSD PCIe4 NVMe that will be mirrored by IBM i.

    Should I be concerned with disk I/O? Any thing I must consider?

    Thank you



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    Adrian Francis Puno
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  • 2.  RE: Migrate to NVME mirrored by IBM i

    IBM Champion
    Posted Tue June 06, 2023 12:25 AM
    Edited by Satid Singkorapoom Tue June 06, 2023 12:27 AM

    Dear Adrian

    This means you will have effectively only ONE disk unit to use in the new machine which means longer disk IO in a single queue even when the disk runs much faster.  The question is whether the faster access time helps prevent too long a disk IO queue or not and this depends on the peak disk IO workload.  If your customer's workload is consistently small with no peak at all, then the case may not be a risky one.

    To get the best information to tell you if you should be concerned about this new disk config or not, you should look at some PDI charts of the current system at the peak workload day.  I see the charts you need to look at are Disk Throughput Overview for Disk Pools and Disk Reads and Writes Detail.   Also look at Wait Overview and Wait by Generic Job or Task and Wait by Subsystem to see if the sum of all disk-related wait time exists in a large amount or not compared to Dispatched CPU Time?  If so, you should have some concern with the new machine.     



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    Education is not the learning of facts but the training of the mind to think. -- Albert Einstein.
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    Satid S.
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    Original Message


  • 3.  RE: Migrate to NVME mirrored by IBM i

    Posted Tue June 06, 2023 01:27 AM

    Hi, an NVMe device will be sub-divided in multiple namespaces, each of those namespaces will be seen by IBM i as an individual "disk arm". This is also those namespaces that will be mirrored with their corresponding namespaces from the other NVMe device. So in my sense, there will be multiple I/O queues. I have many clients who migrated from SAS to NVMe and they are all more then very delighted. The following video is illustrating the namespaces : https://www.youtube.com/watch?v=8z0nnZsGkLE



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    Fabian Michel
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    Original Message


  • 4.  RE: Migrate to NVME mirrored by IBM i

    Posted Tue June 06, 2023 03:56 AM

    Hi ,

     

    IBMi operating system still likes to have at least 8 volumes (name spaces). Don't use only 2 volumes of 1.6TB.

    I don't know what the actual number of IO's are you have on the current system.

    But NVMe internal disks is the best solution for high IO demanding systems.

    I am using now always NVMe disks in new systems.

     

    Have a look to the table below , IBM recommends namespaces of 188GB or 393GB

     

     

    Regards

     

    Paul HEMELEERS

    IBM Power systems technical sales engineer

    Service delivery manager

                      

    T : +32 2 790 82 56― M : +32 496 593 364

    Fax : +32 2 790 84 32

    Leuvensesteenweg 510/B80  1930 Zaventem

    email : paul.hemeleers@econocom.com ― web : www.econocom.com

     

     




    Original Message


  • 5.  RE: Migrate to NVME mirrored by IBM i

    Posted Tue June 06, 2023 11:20 AM

    Hello Adrian, when you work with NVMe you have to create some namespaces into every NVMe (like a volume in FlashSystems or another external storage) . Each namespace have a size, you can use 188GB rather than 393GB for each namespace (remember that IBM i likes a lot to have arms or pseudo-arms in this case).

    Here you can find more information about NVMe.

    Creating NVMe namespaces and adding them to an ASP (ibm.com)

    Managing NVMe - IBM Documentation



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    Juan Martin Araya Carrasco
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    Original Message


  • 6.  RE: Migrate to NVME mirrored by IBM i

    Posted Tue June 06, 2023 09:49 PM

    Thank you everyone for your responses, I now got a good idea with NVME being used as CEC internal disks.

    Especially from the youtube link of Fabian.



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    Adrian Francis Puno
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    Original Message


  • 7.  RE: Migrate to NVME mirrored by IBM i

    Posted Wed June 07, 2023 02:27 AM

    Glad to help! Have fun with your NVMe devices, you will enjoy it for sure!



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    Fabian Michel
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    Original Message


  • 8.  RE: Migrate to NVME mirrored by IBM i

    Posted Wed June 07, 2023 03:31 AM

    Hi ,

     

    One other remark.

    When you have received your system , one name space will already be created used for the load source.

    But this namespace will be one of 800GB. That's not what we want.

    Start your system with dvd ,usb with slic , or tape with savsys in D manual .

    From here you can delete the exiting name space and create a new one (188GB or 393GB) for your load source.

    Be careful , if you have ordered your system with IBM lic pgms preinstalled , you will delete everything with the above procedure.

     

    As Fabian mentioned, you will be surprised of the disk response time and the overall system response time.

    You will not have the time anymore to get a cup of coffee during the first normal IPL ��

     

     

    Regards

     

    Paul

     

     




    Original Message


  • 9.  RE: Migrate to NVME mirrored by IBM i

    Posted Thu June 08, 2023 01:34 PM

    I'm not very familiar with NVMe as I work mostly with external storage, but I suspect you could avoid the IPL to D-Mode and need to reload the OS and licensed programs by:

    With the speed of NVMe, all of this should happen pretty fast, and worse case it fails and you're doing a load from a D-IPL anyway.

    On a brand new install, I'd do all of this without mirroring, then configure the second NVMe and mirror everything later.   Faster and easier.



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    Vincent Greene
    IT Consultant
    Technology Expert labs
    IBM
    Vincent.Greene@ibm.com


    The postings on this site are my own and don't necessarily represent IBM's positions, strategies or opinions.
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    Original Message


  • 10.  RE: Migrate to NVME mirrored by IBM i

    Posted Fri June 09, 2023 02:33 AM

    Hi Adrian

    re concern with disk I/O

    We did a similar migration but with slightly different hardware last year.

    This was  from Power 7 with eight 19A1 283GB 15k in Raid6

    to Power 9 using two EC5B  1.6TB NVMe PCIe3 in RAID1 config.

    As regards production I/O throughput we achieved approx 1.5 times the old system.  But as regards mass updates, backups, startup/shutdown the speed is much more.

    To be realistic IBM i (v7r3) on the old system was running standalone whilst IBM i (v7r4) on the new system in running under VIOS with PowerHA/Geomirror. However the NVMes are attached directly to IBM i.

    Regards

    Edward



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    Edward Camilleri
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    Original Message