Azimout's Linux weblog

Ext3 difference between free and available space

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I have long wondered about this fact, and finally I found out what’s going on:
I always knew that, on ext3 partitions, there’s a slight difference (a few GBytes) between free and available disk space. Then I came across a forum thread that explained the existence of “reserved blocks”, which can only be used by priviledged processes. In fact, if you type man tune2fs, under the -m option you’ll read:

-m reserved-blocks-percentage
Set the percentage of the filesystem which may only be allocated by privileged pro‐
cesses. Reserving some number of filesystem blocks for use by privileged pro‐
cesses is done to avoid filesystem fragmentation, and to allow system daemons, such
as syslogd(8), to continue to function correctly after non-privileged processes are
prevented from writing to the filesystem. Normally, the default percentage of
reserved blocks is 5%.


Written by azimout

08/05/2008 at 17:03

Posted in Reference

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