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How does raid 5 work?

TheGeeker

If I have 4 2tb drives in raid 5 I would have 6tb or storage and one backup. If one drive fails how would the failed drive write to the 4th drive if it failed in the first place? I am confused as to how this works and need some help understanding it.

 Just because you don't care, doesn't mean other others don't. Don't be a self-centered asshole. -Thank You a PSA from the people who do not say random shit on the internet. 

 

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I know what it does. I am saying if a drive FAILS how does the raid get the data off it? If the raid loses a drove how does the extra drive replace the "dead" one?

 Just because you don't care, doesn't mean other others don't. Don't be a self-centered asshole. -Thank You a PSA from the people who do not say random shit on the internet. 

 

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This is the best explanation of Raid5 I've seen. Everything else implies the final drive is used as parity and somehow expects you to believe it all magically goes back together if one fails.

"Epic Voice, Quality Content"

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I know what it does. I am saying if a drive FAILS how does the raid get the data off it? If the raid loses a drove how does the extra drive replace the "dead" one?

Clearly you didn't watch, lol.

Nothing is taken off of the dead drive. It's dead. Rather, another copy of all of that data will be stored across the other 3 drives, and it just copies it over.

"Epic Voice, Quality Content"

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This is the best explanation of Raid5 I've seen. Everything else implies the final drive is used as parity and somehow expects you to believe it all magically goes back together if one fails.

I didn't even watch it. I figured that posting a quick video is easier than me explaining it.

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As the link in Matthew's post describes, for RAID5 often a simple XOR operation is

used to distribute parity information across the drives, then whenever one drive

fails you can work out what should be on that drive by doing some maths on what the

drives you still have are holding.

See also here: https://en.wikipedia.org/wiki/Parity_bit

and here: http://serverfault.com/questions/332634/how-to-calculate-raid-parity-bit

For RAID6, in case anyone cares, the maths is a tad more complex, although the

principle remains the same: Do some maths on the data to calcualte parity, then

put that somewhere else in the array, and in case of any drive failing, reconstruct

what was on that drive by doing the reverse maths on the parity information you

have on the drives which are still working.

https://en.wikipedia.org/wiki/Standard_RAID_levels#Parity_computation

Also some more: http://raid-recovery-guide.com/raid5-parity.aspx

Edited by alpenwasser

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I didn't even watch it. I figured that posting a quick video is easier than me explaining it.

Ah. SOrry I thought it was another here is the raid levels and what they mean vid. I have watched like 10 with no explanation. 

 Just because you don't care, doesn't mean other others don't. Don't be a self-centered asshole. -Thank You a PSA from the people who do not say random shit on the internet. 

 

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As the link in Matthew's post describes, for RAID5 often a simple XOR operation is

used to distribute parity information across the drives, then whenever one drive

fails you can work out what should be on that drive by doing some maths on what the

drives you still have are holding.

See also here: https://en.wikipedia.org/wiki/Parity_bit

For RAID6, in case anyone cares, the maths is a tad more complex, although the

principle remains the same: Do some maths on the data to calcualte parity, then

put that somewhere else in the array, and in case of any drive failing, reconstruct

what was on that drive by doing the reverse maths on the parity information you

have on the drives which are still working.

https://en.wikipedia.org/wiki/Standard_RAID_levels#Parity_computation

Yup, I use Two RAID 6 arrays with 6 drives total.

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As the link in Matthew's post describes, for RAID5 often a simple XOR operation is

used to distribute parity information across the drives, then whenever one drive

fails you can work out what should be on that drive by doing some maths on what the

drives you still have are holding.

See also here: https://en.wikipedia.org/wiki/Parity_bit

and here: http://serverfault.com/questions/332634/how-to-calculate-raid-parity-bit

For RAID6, in case anyone cares, the maths is a tad more complex, although the

principle remains the same: Do some maths on the data to calcualte parity, then

put that somewhere else in the array, and in case of any drive failing, reconstruct

what was on that drive by doing the reverse maths on the parity information you

have on the drives which are still working.

https://en.wikipedia.org/wiki/Standard_RAID_levels#Parity_computation

 

I didn't even watch it. I figured that posting a quick video is easier than me explaining it.

Thanks guys. So I have az97 ar which supports raid 5 but is it better to get a raid card? 

 Just because you don't care, doesn't mean other others don't. Don't be a self-centered asshole. -Thank You a PSA from the people who do not say random shit on the internet. 

 

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