[gpfsug-discuss] File_heat for GPFS File Systems

[Marc A Kaplan]

You asked ...  "We are wishing to migrate data according to the heat onto 
different 
storage categories (expensive --> cheap devices)"


We suggest a policy rule like this:

Rule 'm' Migrate From Pool 'Expensive'  To Pool 'Thrifty' Threshold(90,75) 
Weight(-FILE_HEAT) /* minus sign! */


Which you can interpret as:

When The 'Expensive' pool is 90% or more full, Migrate the lowest heat 
(coldest!) files to pool 'Thrifty', until
the occupancy of 'Expensive' has been reduced to 75%.

The concepts of Threshold and Weight have been in the produce since the 
MIGRATE rule was introduced.

Another concept we introduced at the same time as FILE_HEAT was GROUP 
POOL.  We've had little feedback and very
few questions about this, so either it works great or is not being used 
much. (Maybe both are true ;-) )

GROUP POOL migration is documented in the Information Lifecycle Management 
chapter along with the other elements of the policy rules.

In the 4.2.1 doc we suggest you can "repack" several pools with one GROUP 
POOL rule and one MIGRATE rule like this:

You can “repack” a group pool by WEIGHT. Migrate files of higher weight to 
preferred disk pools
by specifying a group pool as both the source and the target of a MIGRATE 
rule.

rule ’grpdef’ GROUP POOL ’gpool’ IS ’ssd’ LIMIT(90) THEN ’fast’ LIMIT(85) 
THEN ’sata’
rule ’repack’ MIGRATE FROM POOL ’gpool’ TO POOL ’gpool’ WEIGHT(FILE_HEAT)


This should rank all the files in the three pools from hottest to coldest, 
and migrate them 
as necessary (if feasible) so that 'ssd' is up to 90% full of the hottest, 
'fast' is up to 85% full of the next
most hot, and the coolest files will be migrated to 'sata'.





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