About bs= on running dd command

[satimis]

Hi folks,


How to find the value of bs= to have the best erformance of dd in cloning disk image? TIA


B.R.
satimis

[burschik]

Trial and error?

[satimis]

Trial and error?

No error.


On a Virtual Machine running Xen, I run following dd command to clone an image;


# dd if=/path/to/disk.img of=/new_path/to/disk.img bs=4k


It works. But I expect to find out bs=? would have the best result running the above command.


B.R.
satimis

[burschik]

"Trial and error" is a phrase. I think the only way to find an answer is to select a few different values for bs and compare results.

[oz]

Take a look at the dd invocation page. I think it will give you some helpful information.

[secondmouse]

I happened to dd a 60G notebook IDE (5400RPM) HD to another one (whole disk clone) that has the same size and buffer (8MB) and the value I used to bs is 1024K, I also tried 2048K, which didn't improve the speed; and 8096K, which is even slower than when bs=1024K. The time to finish the clone was about 1 hour, with bs=1024K.

[satimis]

Hi folks,


Thanks for your advice.


I'm testing server consoliation on Virtual Machine to clone Guest image. The Guest image size is in the range of 2G~4G. To clone 2 or 3 images I won't spend time on finding the best bs value. If cloning >100 images it is worthwhile spending half hour on it.


B.R.
satimis