[Novalug] need dd help

Jay Hart jhart@kevla.org
Mon Feb 13 17:59:15 EST 2012


You tell me, Don't understand a thing about this, never used it before.

Time between 1st and last vmstat commands about 20 minutes.

[jay@freenas /]$ vmstat
 procs      memory      page                    disks     faults         cpu
 r b w     avm    fre   flt  re  pi  po    fr  sr da0 ad0   in   sy   cs us sy id
 4 0 0    241M  1732M   169   0   0   2   145   0   0   0 11093 22738 9168  2
67 30
[jay@freenas /]$ vmstat
 procs      memory      page                    disks     faults         cpu
 r b w     avm    fre   flt  re  pi  po    fr  sr da0 ad0   in   sy   cs us sy id
 2 0 0    201M  1749M   169   0   0   2   145   0   0   0 11093 22738 9174  2
67 30
[jay@freenas /]$ vmstat
 procs      memory      page                    disks     faults         cpu
 r b w     avm    fre   flt  re  pi  po    fr  sr da0 ad0   in   sy   cs us sy id
 2 0 0    201M  1749M   169   0   0   2   145   0   0   0 11094 22739 9182  2
67 30
[jay@freenas /]$ vmstat
 procs      memory      page                    disks     faults         cpu
 r b w     avm    fre   flt  re  pi  po    fr  sr da0 ad0   in   sy   cs us sy id
 2 0 0    201M  1749M   169   0   0   2   145   0   0   0 11094 22738 9184  2
67 30
[jay@freenas /]$ vmstat
 procs      memory      page                    disks     faults         cpu
 r b w     avm    fre   flt  re  pi  po    fr  sr da0 ad0   in   sy   cs us sy id
 2 0 0    201M  1749M   168   0   0   2   144   0   0   0 11094 22737 9959  2
67 30

> Can you open another shell and run vmstat?  How fast is it writing?
>
> jf
>
> On Feb 13, 2012, at 5:49 AM, Jay Hart wrote:
>
>> After 8 hours, I'm still waiting for the dd command to complete.
>>
>> Jay
>>
>>> Sounds a bit short.  100MB/s write speed would take 10,000 seconds to zero
>>> a
>>> 1TB drive.
>>>
>>> jf
>>>
>>> On Feb 13, 2012, at 12:36 AM, Jay Hart wrote:
>>>
>>>> Not sure I understand what you are saying.  I should take a value such as
>>>> 8
>>>> seconds and multiply by a 1000?
>>>>
>>>> So 8000 seconds should be over 2 hours and 10 minutes.  Sound about right
>>>> to
>>>> zero a 1TB drive?
>>>>
>>>> Jay
>>>>
>>>>> On Sun, Feb 12, 2012 at 10:37:22PM -0500, Jay Hart wrote:
>>>>>> Jon,
>>>>>>
>>>>>> So this will wipe my entire drive, 1k at a time.  1TB will take a while,
>>>>>> I
>>>>>> suspect.
>>>>>
>>>>> Preview it by doing
>>>>>
>>>>> time dd if=/dev/zero of=junk bs=1k count=1048576
>>>>>
>>>>> and multiple the time by 1000.  That should give an outer limit.
>>>>>
>>>>> You could also try
>>>>>
>>>>> time dd if=/dev/zero of=junk bs=4k count=262144
>>>>>
>>>>> and see if there is a speed-up.
>>>>>
>>>>> Running the 1k command on three different systems I got 29,
>>>>> 11, and 3 seconds.  Guess which one had the Solid State Drive :)
>>>>> The 4k command ran about 20% faster.
>>>>>
>>>>> Jon
>>>>>>
>>>>>>> On Sun, Feb 12, 2012 at 10:17:04PM -0500, Jay Hart wrote:
>>>>>>>> I think this command with totally wipe a drive:
>>>>>>>>
>>>>>>>> dd if=/dev/zero of=/dev/devicename bs=1k
>>>>>>>>
>>>>>>>> Yes/no. what exactly does the "bs=1k" do???
>>>>>>>
>>>>>>> By default dd uses input and output buffers of 512 bytes.
>>>>>>> These can be changed individually with ibs= and obs=.
>>>>>>> Your option bs= changes both buffer sizes to 1024 bytes.
>>>>>>>
>>>>>>> I find when making large transfers like this that a
>>>>>>> larger buffer size greatly speeds up dd.  I'd suggest 4k.
>>>>>>>
>>>>>>> jl
>>>>>>> --
>>>>>>> Jon H. LaBadie                  novalugml@jgcomp.com
>>>>>>> 11226 South Shore Rd		(703) 787-0688 (H)
>>>>>>> Reston, VA  20190		(609) 477-8330 (C)
>>>>>>> _______________________________________________
>>>>>>> Novalug mailing list
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>>>>>>>
>>>>>>
>>>>>>
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>>>>>>>> End of included message <<<
>>>>>
>>>>> --
>>>>> Jon H. LaBadie                  novalugml@jgcomp.com
>>>>> 11226 South Shore Rd		(703) 787-0688 (H)
>>>>> Reston, VA  20190		(609) 477-8330 (C)
>>>>> _______________________________________________
>>>>> Novalug mailing list
>>>>> Novalug@calypso.tux.org
>>>>> http://calypso.tux.org/mailman/listinfo/novalug
>>>>>
>>>>
>>>>
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>>>
>>> --
>>> John Franklin
>>> franklin@elfie.org
>>> ICBM: 39º 01' 58.4"N 77º 24' 49.6"W Z+84m
>>>
>>>
>>
>
> --
> John Franklin
> franklin@elfie.org
> ICBM: 39º 01' 58.4"N 77º 24' 49.6"W Z+84m
>
>





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