Why the disk array speed will suddenly slow down

My configuration is AMD X4 955 processor + 770 motherboard + two 500GB hard drives. Recently, the disk array was assembled. When the group was just used, the HDTURN test score was about 180MB/S. But after a few days, the test dropped to an average of 135MB/S.

[Gong Master]: First test whether a single hard disk in RAID is running normally, and whether the RAID system works normally. Secondly, when setting up RAID, you need to select the block size (Block Size). Large blocks are useful for reading large files and large programs, while cell blocks are useful for small file reading and network applications, and vice versa. speed. Users can check whether their block file size is set incorrectly according to their usage.

Block size has a greater impact on RAID speed