This is a semi-production server and I can't bring it down right now. Will try 
to get the monitoring output when I get a chance. 

As I recall, the high CPU processes are brick daemons (glusterfsd) and htop 
showed they were in status D. However, I saw zero zpool IO as clients were all 
hanging.

> On Aug 5, 2018, at 02:38, Raghavendra Gowdappa <[email protected]> wrote:
> 
> 
> 
> On Sun, Aug 5, 2018 at 12:44 PM, Yuhao Zhang <[email protected] 
> <mailto:[email protected]>> wrote:
> Hi,
> 
> I am running into a situation that heavy write causes Gluster server went 
> into zombie with many high CPU processes and all clients hangs, it is almost 
> 100% reproducible on my machine. Hope someone can help.
> 
> Can you give us the output of monitioring these processes with High cpu usage 
> captured in the duration when your tests are running?
> 
> MON_INTERVAL=10 # can be increased for very long runs
> top -bd $MON_INTERVAL > /tmp/top_proc.${HOSTNAME}.txt # CPU utilization by 
> process
> top -bHd $MON_INTERVAL > /tmp/top_thr.${HOSTNAME}.txt # CPU utilization by 
> thread
> 
> 
> I started to observe this issue when running rsync to copy files from another 
> server and I thought it might be because Gluster doesn't like rsync's delta 
> transfer with a lot of small writes. However, I was able to reproduce this 
> with "rsync --whole-file --inplace", or even with cp or scp. It usually 
> appears after starting the transfer for a few hours, but sometimes can happen 
> within several minutes.
> 
> Since this is a single node Gluster distributed volume, I tried to transfer 
> files directly onto the server bypassing Gluster clients, but it still caused 
> the same issue.
> 
> It is running on top of a ZFS RAIDZ2 dataset. Options are attached. Also, I 
> attached the statedump generated when my clients hung, and volume options.
> 
> - Ubuntu 16.04 x86_64 / 4.4.0-116-generic
> - GlusterFS 3.12.8
> 
> Thank you,
> Yuhao
> 
> 
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