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Date: Mon, 5 Nov 2012 19:26:13 -0700 (MST)
From: Warren Block <wblock@wonkity.com>
To: Alexander Yerenkow <yerenkow@gmail.com>
Subject: Re: what's the deal with changing release notes?
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On Sun, 4 Nov 2012, Alexander Yerenkow wrote:

> Can I add my 2c at this point? Where did 10240 appeared from? Did someone
> tried to find some optimal size for most of flashes/cards? I always try to
> use some large number, like 1m or even more. I know by sad experience that
> writing flash with default bs can take much longer than with large bs value.
> Very quick and dirty test (from dev/urandom to 1gb partition on sd card)
> give me that speed numbers (bs, speed):
> 128m = 11,38
> 8m = 11,42
> 512k = 11,46
> 10k = 1,10
>
> So, default advice on how write those images are unoptimised. Drop in speed
> by factor of ten without any reason not god as for me.

Agreed.  The 10K number also looks like a magic number, and it is not. 
Huge buffer sizes don't really improve speed, as your benchmark shows. 
There's no significant difference between 512K and 128M.  I would 
suggest using 64K or 128K for the value.  These are large enough to give 
speed benefits yet still small enough to work even if memory is very 
limited.

Note: FreeBSD's dd is not case-sensitive about unit modifiers, but Linux 
is, so the example should stick to upper case "K".