NFSD high CPU usage

[Adam Guimont]

Rick Romero wrote:
> Are the disks busy before it happens?   I'm far from an expert, but when
> running ZFS with NFS, I've had a lot of issues.  My final resolutions were
> to turn ASYNC off and have log devices and I even have SSD volumes now.
> Otherwise under load the NFS server gets hung up. It never seemed to happen
> on UFS, but due to the number of small files I have, ZFS provides the best
> backup functionality. I'm now trying to move all functions from NFS (to
> more TCP client/server).
>
> You have different info than I've gathered, and it might be because of
> usage. I actively use the system that I've seen NFS dump on, so I see the
> slowness beginning. Once NFS dies, the drive load goes back to normal. I
> wonder, if maybe you are just managing a system for others, and you don't
> see it until after the fact?  Just a thought based on my limited
> experience.

No, the disks are not busy before this happens.

I use the server every day and keep a pretty close eye on it. The disks 
can get busy but it doesn't spike nfsd that much and usually doesn't 
last more than a few seconds.

When this particular issue happens with the nfsd CPU spike, it will last 
until the job running on the client workstation gets killed or when the 
client workstation is rebooted. After that it takes a few seconds for 
the TCP buffers to flush out and allow other clients to connect again.


Regards,

Adam Guimont