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RAID5 on windows7

Tags:
  • NAS / RAID
  • Windows 7
  • Storage
  • Hard Drives
Last response: in Storage
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July 22, 2011 6:23:22 PM

Hi. I just successfully made a RAID 5 configuration using 4 x 1 TB Hard Drives and windows 7. After completing the procedure i can see 2.72 TB of hard disk space. I am a bit confused. As far as my knowledge goes out of the 4 HDDs 2 should be regular storage, 1 for parity and 1 spare so that should make 1.8 TB of visible storage. Why does it show 2.72 TB. Is there any way to see the storage space of Parity drive and the spare drive. Help please

More about : raid5 windows7

July 22, 2011 6:36:55 PM

Storage capacity for RAID 5 is the capacity of all drives (assuming same size) minus 1 so in your case 4 x 1TB = 4TB - 1TB = 3TB storage array capacity, so in your case 2.72 TB is the correct amount. if you were looking to have a hot spare you would need RAID 5+1 then you would have only 2TB storage
Also, parity is not allocated to 1 single disk in most RAID configurations, it is typically striped across all the drives in the array. RAID 5 will have a fault tolerance of 1 drive, RAID 5+1 will have a fault tolerance of 2

hope that helps
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July 22, 2011 6:40:57 PM

can you please explain. How does it have a fault tolerance of 1 when the parity is striped across each drive. In case a drive fails how does it recreate that drive on the spare.
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July 22, 2011 6:48:35 PM

it's pretty technical, but the parity for drive A will be striped to b,c & d, and the parity for B will be a,c & d and so forth so if 1 drive fails, it will recreate the missing data on the replacement drive using the XOR command - - would be easier to explain with this article http://en.wikipedia.org/wiki/RAID

and its not raid 5+1 as i mentioned earlier,, it is RAID 6 that gives you double parity

the procedure to actually rebuild the array i'm not 100% on, however i believe the software/hardware/OS will see the fault, advise you to replace drive and will prompt you through the rebuilding section
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July 22, 2011 6:52:33 PM

Thanks for your help. :) 
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