[SATLUG] RAID5 Recovery - Post Mortem Review - Food For Thought

Samuel Leon satlug at net153.net
Fri Sep 11 18:24:39 CDT 2009


David Labens wrote:
> I've now copied all the data off the RAID5 array - using the copy as a
> backup till I get backups up.  The 1 tb drive has approximately 244 gb
> of data on it (used space), and I've copied ALL the data from the array.
> 
> The array consists of 4 HDDs with 250 GB each, a total array size of approx 1 TB, but approx 750 GB of usable storage space.
> 
> My
> "off the top" conclusion is that the array should have approximately
> 500 GB of free space on it.  But, I'm finding that the numbers don't
> add up.  Note the "Used Dev Size :
> 488391680 (465.77 GiB 500.11 GB)"  And I wonder what that means?
> 
> -----------------------------------
> 
> 
> 
> 
> root at RCH-SERVER:/# mdadm --detail /dev/md0
> 
>    
> 
> /dev/md0:
> 
>         Version :
> 01.00
> 
>   Creation Time : Sat
> Jan 10 13:03:52 2009
> 
>      Raid Level :
> raid5
> 
>      Array Size :
> 732587520 (698.65 GiB 750.17 GB)
> 
>   Used Dev Size :
> 488391680 (465.77 GiB 500.11 GB)
> 
>    Raid Devices : 4
> 
>   Total Devices : 4
> 
> Preferred Minor : 0
> 
>     Persistence :
> Superblock is persistent
> 

I think that is just the size of the raid on the disks.  Actual 
filesystem usage is shown with df -h

Sam


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