[Novalug] need dd help

Jay Hart jhart@kevla.org
Mon Feb 13 19:46:55 EST 2012


Ok,

[jay@freenas /]$ iostat
       tty             da0             ada0             ada1             cpu
 tin  tout  KB/t tps  MB/s   KB/t tps  MB/s   KB/t tps  MB/s  us ni sy in id
   0     1  5.39   0  0.00   1.00 11094 10.83   2.17   0  0.00   2  0 45 23 30

What does this mean???

Jay

> I think whoever said vmstat was thinking iostat..
>
>
>
> Sent with Good (www.good.com)
>
>
> -----Original Message-----
> From: Jay Hart [jhart@kevla.org<mailto:jhart@kevla.org>]
> Sent: Monday, February 13, 2012 03:32 PM Pacific Standard Time
> To: novalug@calypso.tux.org
> Subject: Re: [Novalug] need dd help
>
>
> Now I'm really confused, how does vmstat show the progress towards zeroing
> out
> this drive?
>
> Jay
>
>> 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)
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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
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>>>>>
>>>>>
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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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