On July 26, 2014 9:36:26 AM EDT, Bernhard Voelker
On 07/25/2014 09:05 PM, Greg Freemyer wrote:
For tapes yes, but [...]
Thanks for the insight. So the difference is that mbuffer is reading the input and writing the output at the same time (probably in threads), while dd(1) reads and writes alternately up to bs=.., right?
Have a nice day, Berny
It is more that dd does not have the concept of a high and low water mark. If you set the blocksize to 1.8GB, then dd treats it as all or nothing. So it is not good at smoothing out a dataflow. Buffer lets you have a 1MB block size, but a 1.8 GB high watermark before it starts sending. While sending both dd and buffer will continue reading from the source stream. It is what happens as after the 1.8 GB is sent that is different. dd will say: If internal buffer > 1.8 GB then send it, else wait for 1.8 GB to accumulate. mbuffer will say: If internal buffer > low water mark, keep sending until below low water mark. At least with a tape drive mbuffer's behavior will result in less start and stops which means less wear and tear on the drive and media. Greg -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org