question about io problem

[Dave Cheney]

Certainly under a big io load. I have found in the past that the  
deadline scheduler gives better results than the CFQ scheduler. On  
recent linux kernels you can switch the scheduler on a per device  
basis like this

[root at rado ~]# cat /sys/block/sda/queue/scheduler
noop anticipatory deadline [cfq]
[root at rado ~]# echo "deadline" > /sys/block/sda/queue/scheduler
[root at rado ~]# cat /sys/block/sda/queue/scheduler
noop anticipatory [deadline] cfq

I don't know how much more you can squeeze out of your setup

Cheers

Dave

On 27/05/2008, at 9:31 PM, M.Kursad DARA wrote:

> There is six disks in array.
>
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>           0.28    0.00    3.45    8.87    0.00   87.40
>
> Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz
> avgqu-sz   await  svctm  %util
> sda               0.27     1.09 54.98  3.91   495.61   132.89    10.67
> 0.61   10.35   4.78  28.17
>
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>           3.40    0.00   20.20   71.30    0.00    5.10
>
> Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz
> avgqu-sz   await  svctm  %util
> sda               1.60     2.40 390.20 13.80 32180.80   189.00     
> 80.12
> 16.79   40.52   2.48 100.02
>
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>           3.00    0.00   16.50   62.90    0.00   17.60
>
> Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz
> avgqu-sz   await  svctm  %util
> sda               0.80     0.20 342.00 29.00 26078.40   372.80     
> 71.30
> 15.27   42.47   2.70 100.06
>
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>           3.59    0.00   20.06   67.47    0.00    8.88
>
> Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz
> avgqu-sz   await  svctm  %util
> sda               1.00     0.00 444.51 13.97 31861.08   146.91     
> 69.81
> 14.83   32.27   2.18  99.86
>
> -----Original Message-----
> From: owner-nginx at sysoev.ru [mailto:owner-nginx at sysoev.ru] On Behalf  
> Of
> Dave Cheney
> Sent: Tuesday, May 27, 2008 2:07 PM
> To: nginx at sysoev.ru
> Subject: Re: question about io problem
>
>
> Can you post a few samples of iostat 5
>
> How many disks are in your array ?
>
> On 27/05/2008, at 8:52 PM, M.Kursad DARA wrote:
>
>> Concurrent established ~2000 users.
>>
>> It's SCSI
>>
>> 2 GB memory.  50 Mb is free now.
>> It's not running on VPS
>>
>>
>>
>>
>> -----Original Message-----
>> From: owner-nginx at sysoev.ru [mailto:owner-nginx at sysoev.ru] On Behalf
>> Of
>> Dave Cheney
>> Sent: Tuesday, May 27, 2008 12:49 PM
>> To: nginx at sysoev.ru
>> Subject: Re: question about io problem
>>
>>
>> How many spindles do you have ? What kind of drives? SATA, PATA,  
>> SCSI,
>> FC, etc?
>>
>> How much memory do you have, how much is free at the moment ?
>>
>> Are you running inside a VPS ?
>>
>> Dave
>>
>> On 27/05/2008, at 7:17 PM, M.Kursad DARA wrote:
>>
>>> Centos 5.
>>>
>>> I'm using iostat -x 1
>>> Always see %90
>>>
>>> -----Original Message-----
>>> From: owner-nginx at sysoev.ru [mailto:owner-nginx at sysoev.ru] On Behalf
>>> Of
>>> Igor Sysoev
>>> Sent: Tuesday, May 27, 2008 11:32 AM
>>> To: nginx at sysoev.ru
>>> Subject: Re: question about io problem
>>>
>>>
>>> On Tue, May 27, 2008 at 09:20:12AM +0300, M.Kursad DARA wrote:
>>>
>>>> How can i optimize io on nginx ?
>>>>
>>>> it's serving image and flv files. IO is very high ( %90 )
>>>>
>>>> is there any option to handle it ?
>>>
>>> What OS do you use ? Where do you see 90% IO ?
>>>
>>>
>>> -- 
>>> Igor Sysoev
>>> http://sysoev.ru/en/
>>>
>>>
>>>
>>
>>
>>
>>
>
>
>
>