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5396
October 6th, 2011 08:00
Raid calculation
A RAID 5 group uses the five 300 GB disks 0_0_0 to 0_0_4 for a total user capacity of 825 GB. A customer expands the RAID group with an additional 300 GB disk. What will the total user space in GB be on completion? and why ?
1 ) 1032
2 ) 1093
3) 990 It is wrong
4 ) 1125 It is wrong
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etaljic81
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October 6th, 2011 08:00
Even thought the 6th disk is 300GB in size and the usable space on that drive is ~266GB you cannot just add that space to the first 5 drives' capacity. The 6th drive's usable capacity will shrink automatically since you are creating a RAID Group that contains a disk from the first 5 drives.
Even if you create a RAID Group with drives 0_0_4,0_0_5,0_0_6,0_0_7,0_0_8 you will still only get 1032GB of usable capacity because one of the drives in that RAID Group is a vault drive
dynamox
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20.4K Posts
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October 6th, 2011 08:00
https://community.emc.com/message/458993
Peter_Magdy1
11 Posts
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October 6th, 2011 08:00
Can you please tell me how it is calculated ?
825 + 300 = 1125 GB
etaljic81
1K Posts
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October 6th, 2011 08:00
1032 because of the first 5 disks. The 6th disk's available capacity will be matched to available capacity of the Flare drives
dynamox
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October 6th, 2011 08:00
1032 , those are vault drives
Peter_Magdy1
11 Posts
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October 6th, 2011 09:00
Do you calculated like that
266 - 62 ( private size of flare ) = 204 GB
and 825 + 204 = 1029 ~ 1032 GB
Is that Right ?
Also how 266 GB come from 300 GB ? is the file system use 44 GB ?
Thanks
etaljic81
1K Posts
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October 6th, 2011 10:00
It's more like 268.37GB instead of 266GB.
Your math is close enough (268.37-62=206.37; 825+206.37)
When you format a drive you "lose the capacity." Same thing applies to any drives, laptop or desktop drives. You buy a 500GB drive for your desktop and once you format it you get ~460GB of space. Same thing on the CX