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"Raid is dead" what does that mean?

shirokado
By shirokado
in Storage Devices
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Go to solution Solved by ChineseChef,

A simple ELI5 would be nice , tried googling but couldn't really understand.

 

The long and short of it is that drives are getting larger more rapidly then they are getting faster.  Basically, HDDs have gone from ~100MB/s to ~150MB/s, speed wise.  But they have gone from 1TB to 8TB in that same time.  That means at a speed of 150MB/s, it would take ~14 hours to fill.  But you are unlikely to get that kind of speed while rebuilding an array.  Average real world kind of times, you are looking at 50-80MB/s from a really good RAID card, assuming you are not trying to use the array at the same time.

 

The only real problems are with RAID 5/6, due to parity calculation rebuild times.  During the rebuild, the disks are worked extremely hard, and this is the time when you are most likely to have another failure, since the disks are usually working at 100% for a very long period of time.  This is compounded by the issue that most often these are production arrays, and users and systems still need to get to the data on these disks.  This can cause rebuild times to reach the 1-2 day mark, and that is with smaller drives. 

 

The other issue is that you have a certain likely-hood of a generic data error per X amount of bits read/written.  This use to be no big deal, but we have reached the point where our drives are as big or larger than X.  Meaning you have a near 100% chance of having a bad bit of data, making a rebuild impossible or simply causing data corruption.

 

In summation, the reason people say "RAID is dead", is that rebuild times are getting long enough that even with dual disk fault tolerance, it is not enough.  Combined with the near guarantee of having data corruption, RAID 5 and 6 with large capacity drives is becoming unusable in production(enterprise) environments.

 

RAID 1 is affected in a similar way, but not as dramatically.  This is only due to the usual situations for RAID 1 though.

 

RAID 0 and 1+0 (RAID10) are still good though, and will likely be used for a very long time.  This is because in most places that use these, they understand the risks, and have appropriate data redundancy.  Or at least one would hope.

 

TL:DR:   The drives are getting too big and can't transfer data fast enough.  Plus there is a near 100% chance of having corrupted data.

Posted

A simple ELI5 would be nice , tried googling but couldn't really understand.

Fractal Design Define R4 | MSI x79a-GD45 | 3960X @ 4.6Ghz | Lots of EK Blocks | EVGA GTX780Ti 3GB | Corsair Dominator Platinum 16GB (4x4) DDR3 1866 | Samsung 840 Pro 512GB SSD | Western Digital Red 2TB x4 (Raid 10) | Corsair AX760 | Windows 7 Professional 64-bit

 

 

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Posted

Let it go buddy. Rarely do us mortals understand God's workings. 

But let us pray that Raid is in a better place now. 

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Let it go buddy. Rarely do us mortals understand God's workings. 

But let us pray that Raid is in a better place now. 

Its ded m8 8/8

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  • Solution

A simple ELI5 would be nice , tried googling but couldn't really understand.

 

The long and short of it is that drives are getting larger more rapidly then they are getting faster.  Basically, HDDs have gone from ~100MB/s to ~150MB/s, speed wise.  But they have gone from 1TB to 8TB in that same time.  That means at a speed of 150MB/s, it would take ~14 hours to fill.  But you are unlikely to get that kind of speed while rebuilding an array.  Average real world kind of times, you are looking at 50-80MB/s from a really good RAID card, assuming you are not trying to use the array at the same time.

 

The only real problems are with RAID 5/6, due to parity calculation rebuild times.  During the rebuild, the disks are worked extremely hard, and this is the time when you are most likely to have another failure, since the disks are usually working at 100% for a very long period of time.  This is compounded by the issue that most often these are production arrays, and users and systems still need to get to the data on these disks.  This can cause rebuild times to reach the 1-2 day mark, and that is with smaller drives. 

 

The other issue is that you have a certain likely-hood of a generic data error per X amount of bits read/written.  This use to be no big deal, but we have reached the point where our drives are as big or larger than X.  Meaning you have a near 100% chance of having a bad bit of data, making a rebuild impossible or simply causing data corruption.

 

In summation, the reason people say "RAID is dead", is that rebuild times are getting long enough that even with dual disk fault tolerance, it is not enough.  Combined with the near guarantee of having data corruption, RAID 5 and 6 with large capacity drives is becoming unusable in production(enterprise) environments.

 

RAID 1 is affected in a similar way, but not as dramatically.  This is only due to the usual situations for RAID 1 though.

 

RAID 0 and 1+0 (RAID10) are still good though, and will likely be used for a very long time.  This is because in most places that use these, they understand the risks, and have appropriate data redundancy.  Or at least one would hope.

 

TL:DR:   The drives are getting too big and can't transfer data fast enough.  Plus there is a near 100% chance of having corrupted data.

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-snip-

Thanks, that was actually informative.

Fractal Design Define R4 | MSI x79a-GD45 | 3960X @ 4.6Ghz | Lots of EK Blocks | EVGA GTX780Ti 3GB | Corsair Dominator Platinum 16GB (4x4) DDR3 1866 | Samsung 840 Pro 512GB SSD | Western Digital Red 2TB x4 (Raid 10) | Corsair AX760 | Windows 7 Professional 64-bit

 

 

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