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Old 07-15-2009, 01:16 PM   #1
Quads
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Missing hard drive space?


I just put in a secondary drive, a 1TB. It formatted out to only 917GB, which doesn't seem right, but okay. Its an ext3 file system.

The drive is empty, but it shows 6% used, leaving only 870GB free. Why is that?
 
Old 07-15-2009, 01:58 PM   #2
Wim Sturkenboom
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Hard disk vendors use 1000 for kilobyte while computers use 1024. So Your harddisk is (in computerterms) smaller than what the HD vendor claims; 1000/1024 to the power of 4 is 91% so your 917GB is more or less right.

I don't know the finer details of filesystems, but it makes sense to me that during the formatting information is already written to the disk. Is 6% much? I don't know.
 
Old 07-15-2009, 02:17 PM   #3
David1357
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Quote:
Originally Posted by Quads View Post
The drive is empty, but it shows 6% used, leaving only 870GB free. Why is that?
The used space is overhead for the journal and backup data for superblocks.

Here is an article describing ext3 overhead in more detail.
 
Old 07-15-2009, 02:32 PM   #4
michaelk
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By default ext2/3 filesystems reserve 5% for roots use. This is to help fragmentation and allow root to login if the filesystem becomes full. If its a secondary drive and not / you can safely change reserve space to zero using tune2fs.
 
Old 07-15-2009, 02:49 PM   #5
Quads
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Quote:
Originally Posted by Wim Sturkenboom View Post
Hard disk vendors use 1000 for kilobyte while computers use 1024. So Your harddisk is (in computerterms) smaller than what the HD vendor claims; 1000/1024 to the power of 4 is 91% so your 917GB is more or less right.

I don't know the finer details of filesystems, but it makes sense to me that during the formatting information is already written to the disk. Is 6% much? I don't know.
Yes, I'm aware that the vendors lie, they always have It wasn't the 917GB that had me worried, I was curious where the other forty something gig went to.
 
Old 07-15-2009, 03:25 PM   #6
lazlow
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If the amount being reserved is too much for you and it is not where the / (as in root) partition is, you can change the amount reserved. There have been a number of thread here about how to do this.
 
Old 07-15-2009, 04:21 PM   #7
David1357
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Quote:
Originally Posted by michaelk View Post
By default ext2/3 filesystems reserve 5% for root's use.
It would have been nicer if someone had posted the relevant section from the mkfs.ext3 man page:
Code:
       -m reserved-blocks-percentage
              Specify the percentage of the filesystem blocks reserved for
              the super-user.  This avoids fragmentation, and allows root-
              owned daemons, such as syslogd(8), to continue to function
              correctly after non-privileged processes are prevented from
              writing to the filesystem.   The default percentage is 5%.
The information without an authoritative reference is just information.
 
  


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