[gpfsug-discuss] Initial file placement - first storage pool is now used for data storage (DOC!)

Buterbaugh, Kevin L Kevin.Buterbaugh at Vanderbilt.Edu
Fri Jun 17 17:33:39 BST 2016


Hi Marc,

Read every last one of the thousands of pages of documentation that comprises the GPFS documentation set before doing any GPFS upgrades … yes, I apparently *do* need to do that!  ;-)

The paragraph that I find ambiguous can be found on page 20 of the GPFS 4.2 Advanced Administration Guide (3rd paragraph from bottom):


The placement policy defining the initial placement of newly created files and the rules for placement of

  *   |  restored data must be installed into GPFS with the mmchpolicy command. If a GPFS file system does not

  *   |  have a placement policy installed, all the data is stored in the first data storage pool. Only one placement

policy can be installed at a time. If you switch from one placement policy to another, or make changes to a placement policy, that action has no effect on existing files. However, newly created files are always placed according to the currently installed placement policy.

In my opinion, it should at least contain a pointer the pages you reference below.  Preferentially, it would contain the definition of “first data storage pool”.

Thanks…

Kevin

On Jun 17, 2016, at 11:20 AM, Marc A Kaplan <makaplan at us.ibm.com<mailto:makaplan at us.ibm.com>> wrote:

(Doc?... I ain't about to read a manual!   But just to cover our bases we did stick it into the 4.1.1 pubs)

Policy improvements:
This release includes the following policy improvements:
  ...  (summary of changes, page xv) ...

Implicit SET POOL 'first-data-pool' rule
For file systems that are at or have been upgraded to 4.1.1, the system recognizes that,
even if no policy rules have been installed to a file system by mmchpolicy, data files
should be stored in a non-system pool if available (rather than in the system pool, which
is the default for earlier releases). For more information, see the following:
 Information Lifecycle Management chapter in the IBM Spectrum Scale: Advanced Administration Guide

 ... ( mmchpolicy man page 298) ...
For file systems that are at or have been upgraded to 4.1.1 or later: If there are no SET POOL policy
rules installed to a file system by mmchpolicy, the system acts as if the single rule SET POOL
'first-data-pool' is in effect, where first-data-pool is the firstmost non-system pool that is available for file
data storage, if such a non-system pool is available. (“Firstmost” is the first according to an internal index
of all pools.) However, if there are no policy rules installed and there is no non-system pool, the system
acts as if SET POOL 'system' is in effect.
This change applies only to file systems that were created at or upgraded to 4.1.1. Until a file system is
upgraded, if no SET POOL rules are present (set by mmchpolicy) for the file system, all data will be
stored in the 'system' pool.
For information on GPFS policies, see the IBM Spectrum Scale: Advanced Administration Guide.


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—
Kevin Buterbaugh - Senior System Administrator
Vanderbilt University - Advanced Computing Center for Research and Education
Kevin.Buterbaugh at vanderbilt.edu<mailto:Kevin.Buterbaugh at vanderbilt.edu> - (615)875-9633



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