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Strange varying copying speeds using b120i controller


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i have two wd red drives 3tb in my gen 8 in the first two drive bays via the b120i controller set as raid 0 individual.


Running windows 8.1.


What I notice is that if I copy any large file from one wd drive to the other the copy speed starts off at a blistering 1gb/sec and then after a few seconds it settles down to 100mb/sec and stays at this speed.


If I do the same the other way round the copy speed is around 145mb/sec constant.


Does anyone know why I get this odd behaviour ?


Thanks in advance.

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The 145MB/Sec seems correct as that is the sustained throughput of the Red drives.

So copying drive A to B starts fast and slows. Copying B to A is consistent 145MB/Sec.

Is this true even if you try B to A first?

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hi schoondoggy,


it seems after playing some more the constant 145mb/sec is just the first time copy, if i repeat the process again and again it does also start at a very high speed and come down to 145mb/sec.


So the only odd thing now is why one way is 100 and the other is 145 ?


They are the same model drive purchased at the same time etc.


Maybe there is an updated raid controller driver ?


Thanks anyway.

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Are you booting from drive A?

Also, the really high rate is probably due to the file already existing and it just starts verifying the file.

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It depends on what part of the drive you are saving too



Start of drive 175MB/S End of drive 80MB/S


The 3tb is slower than the 6tb as well

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No i'm  booting from the ODD internal sata port.


Ok nice one i did not know the speed can change across the drive.


Thanks both for your help.

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