[kwlug-disc] [GTALUG] block size for dd -- no difference

[John Van Ostrand]

On Fri, Sep 5, 2025 at 2:27 PM William Park via kwlug-disc <
kwlug-disc at kwlug.org> wrote:

>
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> It seems 1M-8M is the optimum, and also the shortest to type.
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My experience with dd goes back to SCO and HP Unix and includes slow
devices like 60MB tape (taking several hours to write). Lately, the slow
devices are SD cards on Linux. Back then, I found that larger block sizes
than the default worked better, default was something like 512 Bytes. Back
then, a server might only have 8MB of RAM so I doubt I used 1M, more like a
multiple of a block size, like 64K. But with Linux I've been going with 1M
because it was easy to type and I have a lot more than that in total RAM.

In the olden times I figured efficiency meant making sure the device
controller had enough data that it could write efficiency, so keeping a
tape streaming (instead of stop, reposition, then write) or supplying a
disk controller with enough data to write as much of a track as possible.
Today, with no mechanical or analog media limitations, I wonder what
the efficiency could be. Interrupts? System calls?

I'm glad to see my gut feeling and laziness in typing worked for me.
-- 
John Van Ostrand
At large on sabbatical
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