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about fsck

 
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# 1  
Old 06-11-2009
about fsck
i want to know what does it mean by doing a consistentcy check fsck on a disk and why journaling filesystems dont need to do it
and what is meant by disk is in a consistent state when writing because entries are recorded in a journal and then to the metadata and then removed from journal
# 2  
Old 06-11-2009
The secret of UNIX's speed is its buffers... and the main reason you must NEVER turn off a UNIX system by power off - It needs a clean shutdown in order to flush the buffers write to disk any pending write and unmount cleanly all file sytems in order to set the "clean" flag for next reboot...
Total buffer size depends on the system but can reach the GB 400-600 MB is common...

And so after a crash or dirty shutdown, it can take ages at next reboot for the system to come up (yes hours... in fsck...). And then came JFS - what a relief..
There are good books on the subject you know...
To make it simple : See JFS (like VXFS) as a database (oracle?), in case of crash it knows how to recover and if cant totally, will drop the last transaction in order to be in a coherent state...
 
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