[CentOS] Solved Re: imaging a drive with dd

Warren Young warren at etr-usa.com
Fri Mar 3 23:51:18 UTC 2017


On Mar 3, 2017, at 10:49 AM, Lamar Owen <lowen at pari.edu> wrote:
> 
> On 03/02/2017 11:57 PM, Robert Moskowitz wrote:
>> The following worked:
>> 
>> # dd if=/dev/sdb of=cubietruck.img bs=512 count=6268927
>> 
>> 6268927+0 records in
>> 6268927+0 records out
>> 3209690624 bytes (3.2 GB, 3.0 GiB) copied, 114.435 s, 28.0 MB/s
>> 
>> So bs= IS the drive blocksize.
>> 
>> This is the result of trying a number of different values for bs and count.
> 
> You can set bs to a multiple of 512 and it will go a lot faster.

Maybe, maybe not.  OP said he’s on an embedded system, which often implies low-end eMMC or SD type storage, and 28 MB/sec is typical for such things.

When mirroring HDDs and proper SSDs, yes, you want to use large block sizes.


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