hdparm + HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl

Applications Filesystems, Disks and Memory
1

Hi All,
Am finding performance of my SD card using hdparm.

hdparm -tT /dev/BlockDev0

/dev/BlockDev0:
 Timing cached reads:   1118 MB in  2.00 seconds = 558.61 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
ioctl for device
 Timing buffered disk reads:   14 MB in  3.13 seconds =   4.47 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
ioctl for device

Am not aware of "HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device". What actually makes it to occur?? What does this problem mean? How to resolve it??

Thanks in advance.
Amio