2 same drives 2 different speeds

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I have been using a WD Raptor 74gb 16mb cache as my os drive for a number of months and have just acquired another same model Raptor to try raid 0. After running HDTach it is reporting different speeds for the drives.

1st Raptor - max read 85mbps, average 73.4mbps.

2nd Raptor - max read 70mbps, average 64mbps.

Is the difference within tolerance and will it have any effect on a raid set up?

There is approx 40gb of used space on both and I have used WD life tools and reports are fine. Set up is DS3(F10 bios),Geil 2gb,E6300 at stock.

 

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Seems your right bud. My first one is a WD740ADFD and this new one is WD740GD. Rather annoyed about that, had no idea about the platter change. Suppose I will have to sell it on.

 

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Well I set them up in raid0 and getting 125mbs average read and seek of 6.8, so there is a improvement.

Will leave it for a few days and see how it goes.

Thanks for the help. It's much appreciated.