hdparm + Inappropriate ioctl for device

Shell Programming and Scripting
1

Hi All,

Am finding performance of my SD card using hdparm.

Code:
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

2

It is trying to give the SD-card SCSI commands to make sure it doesn't have any lingering cache to mess up the benchmarks. It is an SD-card and thus not remotely SCSI, just acts like it because everything disk-like in Linux is treated like SCSI these days, so can't do those commands, but probably doesn't have a cache to be cleared anyway. Probably fine to just ignore it.