[gpfsug-discuss] File_heat for GPFS File Systems Questions over Questions ...

[Andreas Landhäußer]

Hello GPFS experts,

customer wanting a report about the usage of the usage including file_heat 
in a large Filesystem. The report should be taken every month.

mmchconfig fileHeatLossPercent=10,fileHeatPeriodMinutes=30240 -i

fileHeatPeriodMinutes=30240 equals to 21 days.
I#m wondering about the behavior of fileHeatLossPercent.

- If it is set to 10, will file_heat decrease from 1 to 0 in 10 steps?
- Or does file_heat have an asymptotic behavior, and heat 0 will never be 
reached?

Anyways the results will be similar ;-) latter taking longer.

We want to achieve following file lists:

- File_Heat > 50% -> rather hot data
- File_Heat 50% < x < 20 -> lukewarm data
- File_Heat 20% <= x <= 0% -> ice cold data

We will have to work on the limits between the File_Heat classes, 
depending on customers wishes.

Are there better parameter settings for achieving this?

Do any scripts/programs exist for analyzing the file_heat data?

We have observed when taking policy runs on a large GPFS file system, the 
meta data performance significantly dropped, until job was finished.
It took about 15 minutes on a 880 TB with 150 Mio entries GPFS file system.

How is the behavior, when file_heat is being switched on?
Do all files in the GPFS have the same temperature?

Thanks for your help

 	Ciao

 	Andreas

-- 
Andreas Landhäußer				+49 151 12133027 (mobile)
alandhae at gmx.de