1.
http://www.linux-tutorial.info/modules. ... page=sg_dd
sg_dd
Similar syntax and semantics to dd(1) but does not perform any conversions.
bs=BYTES
this must be the block size of the physical device.
Note that this differs from dd(1) which permits
"bs" to be an integral multiple. Default is 512
which is usually correct for disks but incorrect
for cdroms (which normally have 2048 byte blocks).
2.
http://sg.danny.cz/sg/sg_dd.html
The Linux sg_dd utility
One restriction that sg_dd imposes when either the IFILE or OFILE are accessed via SCSI commands is that BS (i.e. the block size) must match that of the device. Further, if both the IFILE and OFILE are accessed via SCSI commands then BS must match that of both devices.
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