Recovering reserved space from ext4
The Ext4 file system, like Ext3, reserves 5% of the blocks on the file system for the root user. The reserved blocks are there for root’s use as a safe guard if the filesystem gets full, it provides some wiggle room to enable the really important programs to still function. But in some cases there’s not much point in having space reserved for root.
I’ve recently upgrade my workstation with a 6TB internal RAID 0 array for data storage (music, videos, photos, etc) and an external 6TB RAID 0 array as a backup. My OS boot from a 1TB drive. For my 6TB arrays I want the maximum available storage and was interested to see what effect removing the reserved space would have. So, this is what I did.
First I made the Ext4 file system, mounted it and queried how much space was available.
sudo mkfs.ext4 /dev/sdh1 sudo mount /dev/sdh1 /mnt df -h
Looks like I have 5.1TB of available space.
/dev/sdh1 5.4T 186M 5.1T 1% /mnt
Then I unmounted the file system, removed the reserved blocks, checked the consistency of the file system, mounted it and queried how much space was available.
sudo umount /mnt sudo tune2fs -m 0 /dev/sdh1 sudo e2fsck /dev/sdh1 df -h
Looks like I have 5.4TB available now, a saving of 300GB.
/dev/sdh1 5.4T 186M 5.4T 1% /mnt
Now, I could have simply created the files system without the reserved blocks in the first place, but I was interested to see the comparison.
sudo mkfs.ext4 -m 0 /dev/sdh1
Before you start removing the reserved blocks from your ext3/ext4 file systems do a bit a research first.
In: Linux · Tagged with: blocks, Ext3, Ext4, Linux, reserved, space
on January 17, 2010 at 10:24 am
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After tinkering with Ext4 I did some research and testing with other filesystems for my new disk arrays and concluded that XFS (once tuned) is the best filesystem for my needs. My wiki page below explains how I arrived at that decision and how I tune XFS to get optimal performance.
Linux File Systems
on June 11, 2011 at 4:27 pm
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[...] Here is a good tutorial show you how to Recover reserved space from ext4: The Ext4 file system, like Ext3, reserves 5% of the blocks on the file system for the root user. The reserved blocks are there for root’s use as a safe guard if the filesystem gets full, it provides some wiggle room to enable the really important programs to still function. But in some cases there’s not much point in having space reserved for root. [...]