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I am wondering about the pie chart in the properties basic tab. I can see blue is used space and white free space but what does the gray part mean. I have been searching with no luck. Thanks in advanced!

Properties Window

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up vote 9 down vote accepted

By default the file system reserves 5% for the root user, which is what you're seeing in gray. You can change this using tune2fs. For example, to change the reserved space to 1% you would use:

sudo tune2fs -m 1 /dev/sdb1

where /dev/sdb1 is the location of your drive.

I have tested this successfully on Ubuntu 13.10

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Right, that was it, thanks! Anyway I was worried to reduce the reserved space as you suggested but after some digging I found it is fairly safe to do it since it is not the system drive. And while Ext3 is prone to fragmentation and bad performance above 95% usage, Ext4's multi-block allocator is much more fragmentation resistant, as mentioned by Linux filesystem developer and guru Theodore Ts'o: Re: Reserved block count for Large Filesystem – SuperMau Nov 23 '13 at 6:57
+6: Very good answer. – Helio Jul 5 '15 at 9:38

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