hdparm -m16 (Multi Sector) how do you use this option?

Question

Use of -m is VERY DANGEROUS.
Only the old IDE drivers work correctly with -m with kernels up to at least 2.6.29.
libata drives may fail and get hung if you set this flag.
Please supply the --yes-i-know-what-i-am-doing flag if you really want this.
Program aborted.

hdparm -I /dev/sda R/W multiple sector transfer: Max = 16 Current = 8 states that my drive supports multi sector

What is the: --yes-i-know-what-i-am-doing flag Why is this operation so dangerous? Can it be used with SATA - man pages refers to IDE.

Answer 1

Foreword

Multi-sector more only affected drives operating in PIO modes.

Only the old IDE drivers work correctly with -m with kernels up to at least 2.6.29. libata drives may fail and get hung if you set this flag.

• Do you have an IDE drive?
• Do you use an ancient kernel?
• Do you really know what you're doing?

If you answered "yes" three times, then you can go ahead, but then again, you shouldn't have needed to ask this question at all ;-)

Explanation

Kernel developer Alan Cox about multi-sector mode in DMA modes:

In DMA modes the 32bit I/O feature and multi-sector mode are not used.

Source

The thing is that most drives in use today will be set by the kernel to use DMA mode by default...