Gluster users - Aug 2016 - gluster profile mode - showing unexpected WRITE fops

Hi,

I?m doing some benchmarking vs our trial GlusterFS setup (distributed
replicated, 20 bricks configured as 10 pairs).  I?m running 3.6.9 currently. 
Our benchmarking load involves a large number of concurrent readers that
continuously pick random file / offsets to read.  No writes are ever issued. 
However I?m seeing the following gluster profiling output:

   Block Size:              32768b+               65536b+              131072b+
 No. of Reads:                    0                     0               6217035 
No. of Writes:                87967                 25443               4372800

Why are there writes at all?  Are seeks being shown here as writes?

Thanks,
Jackie
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Hi,

How was the profile data collected? Was it a cumulative profile output 
or an incremental profile output?

How did the initial data get written to the 20 bricks, before the read 
workload was started?

What I suspect here is that, you are collecting cumulative output, which 
is possibly showing up the initial writes that were performed to 
populate the volume.

 From the code I do not see seek tracked in iostats, so it is not the 
*seek* that is bloating these numbers up.

Regards,
Shyam

On 08/08/2016 04:47 PM, Jackie Tung wrote:
> Hi,
>
> I?m doing some benchmarking vs our trial GlusterFS setup (distributed
replicated, 20 bricks configured as 10 pairs).  I?m running 3.6.9 currently. 
Our benchmarking load involves a large number of concurrent readers that
continuously pick random file / offsets to read.  No writes are ever issued. 
However I?m seeing the following gluster profiling output:
>
>    Block Size:              32768b+               65536b+             
131072b+
>  No. of Reads:                    0                     0              
6217035
> No. of Writes:                87967                 25443              
4372800
>
> Why are there writes at all?  Are seeks being shown here as writes?
>
> Thanks,
> Jackie
>