Toke me several hours to figure out why the write speed is so slow (not shown previously). It turns out that the Marvell 9123 SATA III controller is much slower for write (127MB/s) than Intel ICH10 SATA II controller (185MB/s) in CrystalDiskMark. I already have the latest driver for Marvell 9123.
Here's an updated read test using Intel ICH10 SATA II controller: