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Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

  • 1.  Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

    Posted 29 days ago

    Dear Team,

     

    Can anyone help me clear the below confusion:

     

    When we model/size the capacity in STORM(Storage modeller Tool), the maximum available array grouping is 14+P+Q (Plus 1 x Hot Spare added by default). That is total no of drives will be 17.

     

    There are 2 queries arise here in my mind:

     

    1. (For Storage Modeller)
    1. What if we want to configure with 18 no of FCM drives (DRAID 6) in STORM tool? ,
    2. Also what will we select in array grouping in the storage modeller?
    3. What is the formula behind this for useable capacity?

    (For Storage GUI)

    1. Is there a limit of array grouping in IBM Flash Storage (5100/5200/7200/9100/9200) during configuration. I mean what if we have 18xFCMs installed in the control enclosure? Do we have the option of configuring with 15+P+Q+ 1 x hot spare (18 Drives)?

     

    If we size with 14+P+Q +1 x hot spare by default, the storage modeller shows the capacity as below:

     

    But if we configure with 14+P+Q the storage modeller shows the capacity as below, how it calculated this capacity:

     

     

    AN EARLY RESPONSE WILL HIGHLY APPRECIATED.. Thanks in advance

     

    Link to Storage Modeller Tool:

    https://www.ibm.com/tools/storage-modeller/#/main

     

    Regards,

    Khurram Saood
    Sr. Platform Solution Specialist


    GBM Pakistan
    T:  +92 21 3432 3801-12 Ext: 233 

     

    M: +923332105300  

    E:  khurram@gbmme.com 


    1st  Floor, Dadex House , 34-A/1, PECHS Block 6 
    Shahrah-e-Faisal, Karachi 75400, Pakistan
    www.gbmme.com

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  • 2.  RE: Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

    Posted 29 days ago
    Khurram,

    The limit of 14+D+P is for the "arrangement" of the array not for the limit of disks on the Distributed Array.
    In the Modeller, you can inform the number of the disks in the DRAID (well beyond 14!) and it will calculate the liquid space in the config. So you can have, for example, a DRAID6 (14+P+Q) with 33 disks -> in this particular case, you will have something like the space of 28 drives for data, the space of 04 drives to parity and the space of 01 drive for spare.
    You can also choose the number of spare drives in the DRAID.

    Regards,


    Asset IT

    www.assetit.com.br
    Claiton Vinícius Zanella
    Diretor Executivo | Asset IT










  • 3.  RE: Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

    Posted 28 days ago
    Thanks Claiton, excellently explained!

    Khurran, important to distinguish here between array width (=total number of drives) and stripe width (= number of data strips covered by P+Q parity strips).
    To be honest, I would struggle myself to advise what would be a reasonable number for the stripe width to use. However, the SpecV GUI eventually makes a good job in making a suggestion that suits your setup.
    Also, IBM's Barry Whyte posted a good article on his blog: Some details about how DRAID works.

    ------------------------------
    Christian Schroeder
    IBM SpecV Storage Support with Passion
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  • 4.  RE: Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

    Posted 28 days ago
    Khurram


    In DRAID, there are no dedicated spare drives that are idle most of the time. All drives in the array process I/O requests always, which improves the overall I/O performance.
    Spare capacity is spread across all member drives to form one or more rebuild areas. So, spare drives in DRAID is a concept (capacity) no a designated drive. In DRAID the spare capacity is called Rebuild area and is equivalent capacity to a single drive. By default is 1, but you can define more than one rebuild area.  The rebuild area does not add usable capacity.
    The grouping is the way the data is stripped in the D (drives): D+P+Q. The quantity of drives impact in how many grouping and grouping type you can do.
    So, you can define 0, 1 or 2 rebuild area
    DRAID6 has a minimum of 6 drives and maximum of 128 drives.
    Distributed array properties
    Redbook sg248492 Implementing the IBM FlashSystem with IBM Spectrum Virtualize V8.4


    Very best regards

    ------------------------------
    Humberto Sosa
    ------------------------------



  • 5.  RE: Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

    Posted 27 days ago

    Hi,

     

    Thank you explaining the capacity concepts on DRAID. Actually I am aware of these facts that you have explained. What I am confused is totally on storage modeller capacity outputs wrt the number of drives when it is exceeded than 17 and available grouping in STORM is max 14+P+Q.

     

    Take this as as a use case that if we need to configure 24 FCM drives then what array grouping we will use as best practices as we have max 14+P+Q. And if we take it then how the storage modeler calculate the capacity what is the formula behind.

     

    The whole point is when the drives are below 18 we can explain the customer the grouping as depicted in storage modeler capacity out put but as it exceeds 17(i.e. 18 or greater ) then customer ask what is the disk distribution and how it is calculated. So we must have any solid formula to explain. Attached below is the screenshot of such example.

     

     

    Khurram Saood
    Sr. Platform Solution Specialist


    GBM Pakistan
    T:  +92 21 3432 3801-12 Ext: 233 

     

    M: +923332105300  

    E:  khurram@gbmme.com 


    1st  Floor, Dadex House , 34-A/1, PECHS Block 6 
    Shahrah-e-Faisal, Karachi 75400, Pakistan
    www.gbmme.com

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  • 6.  RE: Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

    Posted 27 days ago
    Hello Kurrham,

    I understand your concern for the need to explain. After explaining the details how DRAID does work - with distributed parity and distributed spare, I would try to show StorM to the client since there are of course strict formulas, but too many flexibility to explain every single one.

    In setups >16 drives I always use DRAID6, 10+P+Q, never thought about anything alse - not problems so far.

    kind regards
    Konrad Trojok

    Head of Competence Center IBM Storage
    Partner Manager Smartoptics

    #ibmchampion #svagmbh

    SVA System Vertrieb Alexander GmbH
    Dohnanyistr. 30
    04103 Leipzig​

    ​​

    ------------------------------
    Konrad Trojok
    Head of Competence Center IBM Storage
    #IBMChampion #SVA
    ------------------------------



  • 7.  RE: Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

    Posted 27 days ago
    In my understanding, when you define the arrangement DRAID6 14+P+Q and using 1 Spare, you define that each disk will be "sliced" in 17 parts. Each part of the disks will be used in a rotated way, like the picture below.

    Where S1..S14 are the slices of data, P and Q are parity slices and S are spare slices.
    In this particular case, we have:
    - 336x S1..14 - slices of data (24 disks with 14 slices of data)
    - 24x P 
    - 24x Q
    - 24x S

    If you divide the size of disks by the number of slices in each disk, you will have the size of slice. In your case it would be 19.2TB / 17 = 1,12TB per slice.

    So, in this case you should be something like:
    - 336*1,12TB to data = ˜376TB, 
    - 48x1,12TB to parity ˜= 54,21TB or 2,8 disks
    - 24x1,12TB for spare ˜=27,11TB or 1,41 disks 

    From this you can derivate the formula.

    Obviously the numbers will differ slightly from the Modeller as the modeler calculates other things but this is a good way to explain the concept.

    Regards,

    Asset IT

    www.assetit.com.br
    Claiton Vinícius Zanella
    Diretor Executivo | Asset IT











  • 8.  RE: Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

    Posted 26 days ago
    Beautifully explained Clayton.

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    Jorge Escalante
    FlashSystem 5000 Product Manager
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    JORGE ENRIQUE ESCALANTE RAMONET
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  • 9.  RE: Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

    Posted 23 days ago

    Yes , no doubt it was well explained , thanks for the help.

     

    Khurram Saood
    Sr. Platform Solution Specialist


    GBM Pakistan
    T:  +92 21 3432 3801-12 Ext: 233 

     

    M: +923332105300  

    E:  khurram@gbmme.com 


    1st  Floor, Dadex House , 34-A/1, PECHS Block 6 
    Shahrah-e-Faisal, Karachi 75400, Pakistan
    www.gbmme.com

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    Please consider the environment before printing this email.
    Disclaimer: This message and any attachments are confidential and intended solely for the addressee(s).
    Any unauthorized use or dissemination is prohibited.
    GBM Pakistan is not liable for the message if altered, changed or falsified.

     






  • 10.  RE: Maximum Array Width in DRAID 6 using FlashCore modules -Storage Modeller expertise required

    Posted 16 days ago
    Excellent and thanks much Claiton for your explained on this point.

    I have one more question, hope will get the advise from you: What are pros and cons of different grouping formula? (10+P+Q vs 14+P+Q and so on...). Some point need to get advise such as:

    • Write performance of the DRAID array?
    • Read performance of the DRAID array?
    • capacity usage? (look like bigger stripe width or sliced per drive will get more usage capacity)
    • Why we choose 10+P+Q as best practise formula for all FlashSystem product family?
    Thanks and appreciated you can share your thoughts on this.
    Hai.

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    HAI NGUYEN VAN
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