Re: [gentoo-user] Intel(R) C600 SAS Controller

[thegeezer <thegeezer@thegeezer.net>]

On 06/11/2014 12:21 PM, Stefan G. Weichinger wrote:
> Am 11.06.2014 13:18, schrieb thegeezer:
>
>> just out of curiosity, what happens if you do # dd 
>> if=/dev/vg01/amhold of=/dev/null bs=1M count=100 # dd if=/dev/sdc 
>> of=/dev/null bs=1M count=100
>
>
> booze ~ # dd if=/dev/vg01/amhold of=/dev/null bs=1M count=100
> 100+0 Datensätze ein
> 100+0 Datensätze aus
> 104857600 Bytes (105 MB) kopiert, 1,71368 s, 61,2 MB/s
>
> booze ~ # dd if=/dev/sdc of=/dev/null bs=1M count=100
> 100+0 Datensätze ein
> 100+0 Datensätze aus
> 104857600 Bytes (105 MB) kopiert, 2,40518 s, 43,6 MB/s
>
>

ok baffling.
sdc i already said would be slower but not this much slower
it certainly should not be slower than the lvm that sits on top of it!
i can't see anything in the cgroups that stands out, maybe someone else
can give a better voice to this.

all i can think is there is other IO happening
in atop if you can highlight any line that begins LVM CPU or DSK and
paste it in to a reply - with no virtualmachines running and no dd or
anything.
then run a dd as before and highlight the lines in atop while it is
running (maybe increase count to 1000 to give yourself a chance) and
paste in here too