Root normally reserves space on a partition to prevent the disk filling up totally and crashing the system, but that's normally just 5%, so where's the other 5% (100GB) going? You can check how much space is "reserved" for root with:
With this in mind, how do you figure such a large space consumption for overhead? I interpret that as minimal and normal overhead -- formating factors, etc.
In fact, on my 30G physical drive as a single partition it reports a filesystem size of 27.94G (a loss of ~7% due to the differences in the way it is stated + overhead)
You'll note that that 1000/1024 is just about 2% short. That should be all you lose to disk naming conventions, but you may lose other space to (as others mentioned) inodes, overhead, etc. So you get to 27.94GB *filesystem size*. But if you add the "used" and "available" numbers from "df -m", do they add to that? Mine don't... they add up to about 5% less than the filesystem size. That's the reserved blocks.
On one disk I could check very quickly, I have this (edited for brevity):
root@rita [~]# df -m Filesystem 1M-blocks Used Available Use% Mounted on /dev/hda2 55236 29532 22898 57% / /dev/hda1 99 7 86 8% /boot none 243 0 243 0% /dev/shm
root@rita [~]# tune2fs -l /dev/hda2 Filesystem OS type: Linux Inode count: 7192576 Block count: 14366126 Reserved block count: 718306
718306 reserved blocks is nearly exactly 5% of the total number of blocks. And note that 22898 + 29532 (used + available) is 5.08% less than 55236 (the number of blocks in the filesystem). Now, let's make some changes!
1. Here's the original setup:
root@rita [~]# df -m Filesystem 1M-blocks Used Available Use% Mounted on /dev/hda2 55236 29532 22898 57% / /dev/hda1 99 7 86 8% /boot none 243 0 243 0% /dev/shm
2. Reduce the reserved blocks percentage to 3%:
root@rita [~]# tune2fs -m 3 /dev/hda2 tune2fs 1.27 (8-Mar-2002) Setting reserved blocks percentage to 3 (430983 blocks)
3. The results:
root@rita [~]# df -m Filesystem 1M-blocks Used Available Use% Mounted on /dev/hda2 55236 29532 24020 56% / /dev/hda1 99 7 86 8% /boot none 243 0 243 0% /dev/shm
You'll note that the filesystem size has not changed, and the used space has not changed. BUT, more space is available because we have fewer reserved blocks. Checking again, 24020 + 29532 = 53552, which is 3.05% less than the filesystem size.
4. Put things back to normal:
root@rita [~]# tune2fs -m 5 /dev/hda2 tune2fs 1.27 (8-Mar-2002) Setting reserved blocks percentage to 5 (718305 blocks)
root@rita [~]# df -m Filesystem 1M-blocks Used Available Use% Mounted on /dev/hda2 55236 29532 22898 57% / /dev/hda1 99 7 86 8% /boot none 243 0 243 0% /dev/shm
So, the loss of space to which you refer is independent of, and additional to, the one I mentioned. In reality,
* Filesystem size = used + available + reserved
* Disk space = filesystem size + overhead
We are both right. <grin>
-- Rodolfo J. Paiz rpaiz@xxxxxxxxxxxxxx http://www.simpaticus.com
