Hi list,

     What is time between call dd? On ext filesystems is implemented 
delay before physically write date on disk. It's for e.g. minimally 
files fragmentation. Second question is that, did you try call "sync" 
command after each of writes?

---
Best regards,
Jakub Juszczakiewicz
Krypto-IT

W dniu 2022-06-23 14:27, Radisson via Dng napisał(a):
> Its a normal HD i guess 4096 is ok,
> but i do not think that this matters.
>
>
> Am 23.06.22 um 13:11 schrieb Rich W:
>> Hi,
>>
>> A blocksize of 1G seems extreme.
>> What is the optimal blocksize of the output device?
>>
>> Cheers,
>> -Rich
>>
>>
>> On Thu, Jun 23, 2022, 4:52 AM Radisson via Dng <dng@???>
>> wrote:
>>
>>> Hi list,
>>> i found a strange ext4 (?) effect.
>>>
>>> when i write to a disk:
>>> dd if=/dev/zero of=xx bs=1G count=1
>>>
>>> reports 2.6 GB (expected)
>>> doing again speed drops to 200MB.
>>>
>>> removing xx restores old speed.
>>>
>>> I ask the net and it seems that the effect is there
>>> since kernel 2.6. I found the explainations a bit confusing.
>>>
>>> does anyone know more ?
>>>
>>> note: i was analysing a performace issue for mysql and i am
>>> not sure if that problems matters outside tests.
>>>
>>> re
>>> rp
>>>
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>>
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