IO Wait very high and real IO speed is very low

[Tang Jianwei]

Hi Marty,

     Thank you very much for your time and help, here is the output of 
$dstat
     http://pastebin.com/kiHijEKY

Best Regards
Tomas
On 2014/3/1 23:52, Marty Sweet wrote:
> Hi Tomas,
>
> Re-reading your original messages: If the system is experiencing lots
> of IO it will appear as wait %, this can also be seen by processes
> excessively in D state.
> It appears (looking at kern.log) that processes are getting blocked
> from disk, which obviously isn't ideal.
>
> Does this happen at set intervals?
>
> I have greped out the D state processes here: http://pastebin.com/b04bgHbL
>
> Could you run $ dstat and send a 10 lines when the issue occurs. This
> will allow us to tell the traffic being written to disk / read from
> network and the loads of the system.
>
> Marty
>
> On Sat, Mar 1, 2014 at 4:16 AM, Tang Jianwei <myhnet at gmail.com> wrote:
>> Hi Marty,
>>
>> thank you very much for your reply and the following is the files you are
>> asking
>>
>> /var/log/kern.log (should be the same as what you were asking)
>> http://pastebin.com/3fC1qxrq
>>
>> /var/log/dmesg
>> http://pastebin.com/G059cxXN
>>
>> output of the commands
>> http://pastebin.com/6faPXt43
>>
>> And thank you very much in advance for your great help.
>>
>>
>> Best Regards
>> Tomas
>>
>> On 2014/2/28 20:00, ubuntu-users-request at lists.ubuntu.com wrote:
>>> Message: 3
>>> Date: Fri, 28 Feb 2014 08:00:31 +0000
>>> From: Marty Sweet <msweet.dev at gmail.com>
>>>
>>> To: "Ubuntu user technical support, not for general discussions"
>>>          <ubuntu-users at lists.ubuntu.com>
>>> Subject: Re: IO Wait very high and real IO speed is very low
>>> Message-ID:
>>>
>>> <CALoaWF5ACbWc=wwEiv4WorQZu0gpSEpk0UUSLMX6QhqnO1-m+w at mail.gmail.com>
>>> Content-Type: text/plain; charset=ISO-8859-1
>>>
>>>
>>> Hi Tomas,
>>>
>>> Could you provide the output of /var/log/kernel.log and /var/log/dmesg
>>> and $ df -h and $ fdisk -l ?
>>> When the problem occurs, can you also run $ ps aux ?
>>>
>>> Once you have done this please post it on pastebin and send the link,
>>> as there will be a few hundred lines.
>>>
>>> Thanks,
>>> Marty
>>>
>>> On Fri, Feb 28, 2014 at 6:00 AM, Tang Jianwei <myhnet at gmail.com> wrote:
>>>> Hi All,
>>>>
>>>>       recently I get a very weird problem from my Ubuntu Server 1204 LTS
>>>> 64bit:
>>>>       1. the write speed can reach 500MB/s when there is no other
>>>> processes
>>>> running
>>>>       2. the write speed down to around 10MB/s when there are many other
>>>> processes and meanwhile:
>>>>               a. only very high usage from io wait
>>>>               b. sys, user and all the other cpu usages are very low
>>>>               c. the system load average can reach to 15 and even more
>>>> higher
>>>>
>>>>       can any one give me some advice what is wrong with my system, and
>>>> what I
>>>> should to adjust in hardware/software?
>>>>
>>>>       the platform is:
>>>>       MB: Intel S3240GPLC
>>>>       CPU: I3-540
>>>>       RAM: Kingston 4G ECC
>>>>       Storage: LSI MegaRaid 9270-8i, Raid 5 with 5 drives + 1 spare,
>>>> ForcedWB
>>>> with no BBU
>>>>       Drive: WD 3T
>>>>
>>>>
>>>>       thank you very much.
>>>>
>>>>
>>>> Best Regards
>>>> Tomas
>>>>
>>>>
>>>>
>>>> --
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>>>
>>>
>
>