We have a similar issue but different numbers. We will have one controller that is showing 100% cpu busy but when doing the sysstat -M all of the processors are showing fairly low usage. The Kahuna task is in the 80-90 plus percent. mostly the users don't seem to be affected but administrative tasks are definitely affected. For instance, the status displays in OnCommand will have gaps in reporting latency or I/O or throughput etc. In my searching I haven't found a clear answer of what is happening (other than background tasks) and have gotten no information about how to try to determine what is happening or how to limit whatever tasks are causing so much CPU busy. Granted the number is not an obvious problem since each CPU is not high usage but it's definitely affecting what is happening with the system.

Kelley R. Green
IT Specialist
Global Technology Services - Storage
Cell 801-916-1273
e-mail: krgreen@us.ibm.com

From: Martin Leggatt <martin@leggatt.me.uk>
To: Jeff Mohler <speedtoys.racing@gmail.com>,
Cc: "toasters@teaparty.net" <toasters@teaparty.net>
Date: 04/05/2014 01:31 PM
Subject: Re: CPU usage and HA
Sent by: toasters-bounces@teaparty.net

Hi Jeff,

I ask as we have a Filer that isn't experiencing any performance issues from the client perspective but is showing each controller over 50% intermittently.
I'm not clear if this is because the Filer isn't busy and is doing background tasks or if it is genuinely busy (perfstats just show the Kahuna domain busy).

In the past Netapp have said that if both controllers CPU is over 50% then the Filer is not HA and an upgrade should be considered (obviously they want to sell Filers)

As you said it's not possible to confirm if this is an issue without failing the controller over and confirm if there is any latency issues on the clients.

I just think its incorrect to say a Filer that has both controllers over 50% CPU intermittently is not HA and requires an upgrade.

In my environment HA is to provide a 100% seamless service where there is zero impact but its difficult to justify testing this on a production system.

Martin

On 04/04/2014 18:17, Jeff Mohler wrote:
CPU is a pretty poor measure of performance to the user workload..but it depends(tm) what you wanna do.

Do you think HA is to provide a 100% seamless service where there is zero impact.
-or-
Do you think HA is to provide services in the case of a failure, where there may be additional latency, but you are _still working_.

Either way, consistent HA testing (yearly?) will help you track the resiliency of your HA solution...because honestly CPU is not the best way to look at this, at least by itself.

On Fri, Apr 4, 2014 at 7:15 AM, Martin <martin@leggatt.me.uk> wrote:
I know that if a Filer is not busy serving data it will run background task
at a higher priority that will use the spare CPU while the Filer is not
under load.

In an active/active config the Filer CPU shouldn't be over 50% on each
controller as above this the Filer is not longer HA.

My question is if a Filer is showing low latency and isn't busy but its CPU
is at 50% on each controller is this an issue?

I'm not clear if you have two controllers showing 40/50% CPU due to
background tasks that isn't busy whether it will still be HA if one
controller were to fail? My thinking is those background tasks will just run
at a lower level (some may not run in failover state??)

--
View this message in context: http://network-appliance-toasters.10978.n7.nabble.com/CPU-usage-and-HA-tp25641.html
Sent from the Network Appliance - Toasters mailing list archive at Nabble.com.
_______________________________________________
Toasters mailing list
Toasters@teaparty.net
http://www.teaparty.net/mailman/listinfo/toasters

--
---
Gustatus Similis Pullus
_______________________________________________ Toasters mailing list Toasters@teaparty.nethttp://www.teaparty.net/mailman/listinfo/toasters