5 Replies Latest reply: Aug 27, 2013 12:08 PM by wnorthmtitsd RSS

Flash Pool limitations

wnorthmtitsd Sprinter
Currently Being Moderated

I have been trying to find some definitive information on flash pool limitations related to ontap 8.1.2/8.1.3 and 8.2

and related to the FAS3250.  However I cannot find anywhere that states what the size limitations are, nor the

number of flash pools that can be on a single controller.

 

I have heard that there is a 2T per array, 1T per controller, and only one aggregate can have a flash pool.

 

Can someone point me to a netapp document that spells it out ?

 

thanks!

 

---- walter

  • Re: Flash Pool limitations
    dcornely1 Cyclist
    Currently Being Moderated

    Start with this document:

    http://www.netapp.com/us/system/pdf-reader.aspx?m=tr-4070.pdf&cc=us

     

    Most questions will be answered.  One that isn't (and I consider important) is what qualifies an I/O as random vs. sequential.  From what I've been told, an I/O that is less than 16K in size is considered random - important because Flash Pools only cache random I/O (as explained in the document I linked to above).  Also, check the Hardware Universe here:

    https://hwu.netapp.com/Home/Index

     

    It will show you how much SSD a given HA pair can can accommodate while running CDOT.  For the 3250 per the Hardware Universe it is 4TB.

     

    Hope this helps...

    • Re: Flash Pool limitations
      pascalduk Kart Racer
      Currently Being Moderated

      dcornely1 wrote:

       

      Most questions will be answered.  One that isn't (and I consider important) is what qualifies an I/O as random vs. sequential.  From what I've been told, an I/O that is less than 16K in size is considered random - important because Flash Pools only cache random I/O (as explained in the document I linked to above). 

       

      I see on my install base with, flexscale.lopri_blocks set to off, average read request sizes from Flash Cache that are over 16KB. I therefore think it is less than 32KB.

       

      You can calculate the average request size from e.g. the "stats show -p flexscale-access" output.

    • Re: Flash Pool limitations
      wnorthmtitsd Sprinter
      Currently Being Moderated

      Thanks,

      I looked at 4070  and it doesn't answer my questions, tho it should.

       

      I don't see in the hardware universe where it refers to the max ssd.

      Which is also affected by the ontap version, not just the hardware itself.

       

      ---- walter

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