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Old 05-14-2013, 11:36 AM   #1
eje4
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RHEL6 post-installation partition-size discrepancy


Hello,

I'm a newcomer to RHEL and I'm installing RHEL6 for the first time, on a Dell PowerEdge server with three 3-TB drives, configured in a RAID 5 setup. With the RAID 5, the total of 9 TB should become effectively 4.5 TB of file storage capacity. But after I installed RH and checked the partition sizes using dh, I'm not getting nearly as much disk space showing up as I should. What happened to all of the space I was supposed to get? Here is the output from a df:

size used avail use% Mounted on
/dev/mapper/vg_buccal-lv_root 50G 1.8G 45G 4% /
/mpfs 3.9G 0 3.9G 0% /dev/shm
/dev/sda3 485M 37M 423M 9% /boot
/dev/mapper/vg_buccal-lv_home 1.8T 196M 1.7T 1% /home

I would expect that I ought to be getting over 4TB in /home. So what's going on? I would appreciate any guidance and advice on this. Thanks,

Eric
 
Old 05-14-2013, 12:42 PM   #2
TobiSGD
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Quote:
Originally Posted by eje4 View Post
With the RAID 5, the total of 9 TB should become effectively 4.5 TB of file storage capacity.
Nope, RAID 5 has a space efficiency of (1-1/n), so with 3 3TB disks you get 6GB disk space: (1-1/3)*9GB.

Quote:
Here is the output from a df
df only shows mounted partitions, so it may be possible that you have not mounted all partitions or you have not partitioned all of the available space. Have a look at the output of
Code:
parted -l
It will show the disk sizes and the partitions, even if they are not mounted.
 
Old 05-14-2013, 08:06 PM   #3
chrism01
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As per TobiSGD, I'd expect 6TB; see
https://en.wikipedia.org/wiki/Standard_RAID_levels
https://en.wikipedia.org/wiki/RAID
 
  


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