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A friend of mine has a T530 (I think he bought it last year) and I checked the spec it seems to support RAID 1 (mirroring). He currently has one hard disk running and is considering RAID 1 and is also considering buying a SSD as a faster drive. I don't have much knowledge on either.

Two questions:

  1. Is it possible to use SSD as THE drive and use the current disk as the mirror?

  2. If it is possible, would performance benefit he would have gotten from using the SSD versus that of the hard disk be throttled to the speed of the disk because the system has to make sure the mirror integrity?

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When creating RAID arrays it is crucial to have identical devices. If you have asymmetric devices, I don't think you will get the full performance benefit of both. Your bottleneck on writing will still be the slowest one. On reading, you may notice a factor of 2 improvement from the slowest speed.

In the setup you are mentioning, your performance will still be limited by the old hard-drive. The only advantage you will gain is that of having a replica backup of your HDD just in case anything get messed up with it.

If he wants real performance gain, he should buy 2 SSDs and replace the original drive.

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This advice is not neccessarily incorrect. I can't speak for Windows, but Linux software raid has no problem with different size drives - as long as the partitions being raided are about the same size if you dont want to waste space. You can still get fast read performance with an SSD + HDD, and even boost your write performance (but not to SSD levels) with certain RAID strategies. –  davidgo Apr 12 '13 at 4:04
    
At the end of the day, it is not worth it at all to pair an SSD + HDD into a RAID. He better gets another HDD for cost efficiency (and he will not get better performance than this), or get two SSDs. Other than this, I will say it is a waste of money. Definitely, RAID will work with any devices combination and will adapt to it, but it will not give you the estimated performance. –  Bichoy Apr 12 '13 at 4:10
    
Software permitting he CAN get better performance with RAID SSD + HDD then 2 x HDD, particularly for reads. Have a look at my performance tests for my setup - which does this - in an intelligent way (in Linux) - my.host.net.nz/blog/2012/09/… –  davidgo Apr 12 '13 at 6:00

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