I have a system with over 10,000,000 files where I want to track the disk usage of a couple of users (these users own the millions of files). Based on the following Q&A http://stackoverflow.com/questions/4307692/fastest-way-to-calculate-directory-sizes I want to look into linux disk quotas for this job since the du command also takes over an hour to run on my system.
My question is:
1) What is the expected run time of repquota? is it always very fast (eg. run in under 1 minute)? or does it depend on the number of files and disk size being tracked?
2) do I need to run quotacheck to update the quata information (files? database?) to change the output of repquota? or will repquota always give me up-to-date information?
Example for 2): If I run the following commands what is the expected output:
repquota /tmp head -c 1024 /dev/urandom > /tmp/new.file sleep 1 repquota /tmp
3) Will the second repquota /tmp give the same output as the first? or will the quota info be updated only because I wrote to the disk (and not based on running some other background quota updating program)?