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Old 08-29-2007, 08:08 PM   #1
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Question Software RAID - where is all my space?

Hi All,

I have used mdadm to set up a RAID5 system using 3x500GB drives.

~# cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid5 hdd1[2] hdc1[1] hdb1[0]
      976767872 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
unused devices: <none>
Upon creating an etx3 filesystem and mounting, I see that I have about 50 GB missing from the filesystem!

/share# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda1             3.8G  573M  3.0G  16% /
varrun                 62M   48K   62M   1% /var/run
varlock                62M     0   62M   0% /var/lock
procbususb             62M   76K   62M   1% /proc/bus/usb
udev                   62M   76K   62M   1% /dev
devshm                 62M     0   62M   0% /dev/shm
/dev/md0              917G  200M  871G   1% /share

/share# ls -lah
total 24K
drwxr-xr-x  3 root root 4.0K 2007-08-30 10:35 .
drwxr-xr-x 22 root root 4.0K 2007-08-30 10:38 ..
drwx------  2 root root  16K 2007-08-30 10:35 lost+found
Note that the fs is currently completely empty. Where has the extra space gone??
Old 08-29-2007, 09:16 PM   #2
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The ext3 filesystem reserves approximately 3% of available space for system use. That 3% doesn't show up as available, therefore it appears that you have missing disk space.

Note that 3% of 3x500 gig comes out to 45 gig.
Old 08-29-2007, 11:22 PM   #3
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Thumbs up

Ah Yes that was it. I knew that ext3 reserved some space but I never thought it to be such a large volume. Using tune2fs to change reserved blocks to 1% has made a difference.



raid, software

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