[gpfsug-discuss] Clarification about blocksize in stardanrd gpfs and GNR

david_johnson at brown.edu david_johnson at brown.edu
Thu Mar 21 13:32:04 GMT 2019


The underlying device in this context is the NSD, network storage device. This has relation at all to 512 byte or 4K disk blocks. Usually around a meg, always a power of two. 

  -- ddj
Dave Johnson

> On Mar 21, 2019, at 9:22 AM, Dorigo Alvise (PSI) <alvise.dorigo at psi.ch> wrote:
> 
> Hi,
> I'm a little bit puzzled about different meanings of blocksize for different GPFS installation (standard and gnr).
> 
> From this page https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/General%20Parallel%20File%20System%20(GPFS)/page/File%20System%20Planning
> 
> I read:
> The blocksize is the largest size IO that GPFS can issue to the underlying device
> A subblock is 1/32nd of blocksize. This is the smallest allocation to a single file
> For non-gnr GPFS device is quite clear to me (I hope): it is a single spinning disk (or ssd). And I verified this on a small cluster composed of nsd using their local hard drive.
> 
> Can someone explain what is the "device" in the case of GNR ? a single pdisk ?
> 
> Thanks,
> 
>   Alvise
> 
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