I was writing to /dev/null. It doesn't seem to have an issue.

This appears to be related to "iflag=direct" more than anything.

W/o direct it works, but, for example I can't use iflag=direct with /dev/zero
for even a 4K block size.

Hmmm....

Paul Eggert wrote:

On 10/12/2012 02:14 AM, Pádraig Brady wrote:

if you specify ibs and obs seperately,
then you will get writes of the size you requested at least.


Won't there be similar problems with the write system
call too?  Perhaps not on Linda's system, but on other
systems.  Once the buffer size exceeds 2 GB or so,
things get pretty dicey in the wild, not due to any
problem in dd itself, but due to the kernels or
file systems that dd relies on.