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[Linux-cluster] GFS & journal resources ... common ratio?



I just have a quick question regarding the amount of storage occupied by the journals. Is there a common ratio to determine how much space will be occupied?

I’m doing very rough map and experimenting with different conditions, but I can’t seem to get a common mechanism for predicting the usable storage limit given the number of locks.

 

Currently we have an 8 node cluster with 9 journals defined (+1 just in case)…  We are awaiting the external storage hardware; but in the time being I am using exporting iscsi drives from another machine to work with.

 

With 9 locks and creating a 1.75GB partition, I get 655 MB usable from it…. (roughly calculated ratio: 3.37)

With 9 locks and creating a 1.50GB partition, I get 393 MB usable from it…. (roughly calculated ratio: 2.36)

With 9 locks and creating a 1.25GB partition, I get 131 MB usable from it…. (roughly calculated ratio: 0.90)

 

I’m obviously missing a figure during my calculations because the ratios vary each time… I’d have expected them to be a bit more constant…

At the end of the day I want to be able to know ahead of time how much hard-disk space I need to allocate for ‘X usable’ based on the number of locks I’m using.

 

The simple equation I used was:

X/9=USABLE/ALLOCATED

 

ie: (X/9=.655/1.75 = 3.369)

 

 

Chris


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