Raid 5 - 7 drives as good as 8?

["Jennifer Wilson" <jennifer.wilson@xxxxxxxxxxxxxxxxxx>]

Hi,

Trying to get my head round installing some more drives on our Model 170.

Currently has 6 x 4GB drives in RAID 5 with parity spread across 4 drives

so -

              Size    %  
 Unit  Type    (M)  Used 
    1  6607   4194  80.5 
    2  6607   3145  80.3 
    3  6607   3145  80.8 
    4  6607   3145  80.7 
    5  6607   3145  80.3 
    6  6607   4194  80.3 

I have 2 more 4GB drives waiting to go in but I'm unsure as to whether when I 
add the 8th drive will parity automatically get spread across all 8 drives 
rather than 4?

If so that means with 7 drives I get 25.1GB (4 drives at 3145 and 3 drives at 
4194 utilisation)
and with 8 drives I get 25.1GB (8 drives at 3145 utilisation)

Is this correct?

Thanks,

Jennifer.

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