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Re: [Linux-cluster] Behavior of "statfs_fast" settune





For GFS1, we can't change disk layout so we borrow the "license" file that happens to be an unused on-disk GFS1 file. There is only one per file system, comparing to GFS2 that uses N+1 files (N is the number of nodes in this cluster) to handle the "df" statistics. Every node keeps its changes in memory buffer and syncs its local changes to the master (license) file every 30 seconds. Upon unclean shutdown (or crash), the local changes in the memory buffer will be lost. To re-sync the correct statistics, we need to use real "df" command (that scans the on-disk RGRP disk structures) to adjust the correct statistics. For details, check out one of my old write-ups in:

http://people.redhat.com/wcheng/Patches/GFS/readme.gfs_fast_statfs.R4


BTW, I'm not very happy with this implementation and there are few other ideas on the table. However, since GFS2 is imminent (I hope), will keep the code as it is today.
-- Wendy



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