Existing situation are four hard disk raid 1, two partitions, a system, a database, database partition now want to improve the IO performance, the premise is don't want to clear data to redeploy do raid5, so bought 15 K high performance hard disk 600 g, before is 300 g 7.5 K, this kind of circumstance, can change each 15 K 600 g hard disk? (a 300 g hard disk 7.5 K, 15 K on 600 g hard disk, data synchronization is completed, in another piece of 300 gb hard drive, 600 g hard disk) that can replace the existing raid 1 support? Completely replaced after play the performance of the new hard disk 600 g 15 k? Or capacity is 300 g, IO can achieve better performance? Give advice or comments please!