2012-08-31 11:32 AM - last edited on 2016-06-30 03:59 PM by Li-Jacques
I just installed ONTAP Edge and it runs 100% CPU across both CPU's as shown in vCenter but when I run sysstat in the console it shows 0% to 1% CPU utilization. Is this normal behavior? Will ONTAP Edge always burn 2 cores?
2012-09-02 06:58 AM
As others have stated this is expected: Data ONTAP Edge requires two cores for operation. This is architectural requirement for Data ONTAP and reducing the resources available will lead to adverse behavior in WAFL.
The reason VMware shows the CPUs at 100%, but sysstat shows something which is more accurate with regard to the current load on the system, is how VMware scheduling interprets the activity of the CPU. Data ONTAP does not perform the halt CPU instruction when idle and this makes the idle thread appear to be hot on a vCPU. This leads to VMware always reporting 100%. Our performance measurements found that performing the halt instruction when idle had a definite impact on total IOPS for various tests. Not performing halt when idle is the same behavior as on physical NetApp filers.
It was unclear from your post if you are talking about the evaluation version of Data ONTAP Edge or the production version. The production version enforces a CPU and memory resource reservation for the virtual machine. This ensures that Data ONTAP Edge will always get two vCPUs and 4GB of memory.
I hope this helps.
2012-09-02 04:54 PM
I tried to double the allocate more resources to the ONTAP-v virtual machine increasing ram from 4GB -> 8GB and 2 vCPU to 4vCPU.
NetApp has checks on boot and the virtual machine fails to boot anymore? Will increasing resources make performance any better?
2012-09-09 07:36 AM
I'd hardly describe this as 'normal behaviour' - it may be expected by Netapp but for everyone else it's likely to be a problem for various reasons;
This wasn't the case for the Netapp Simulator which has been around for years. What's changed? NT4 running multiple processors used to have this issue too but I assumed we'd left that kind of problem behind years ago. I tried putting this in my lab which only has two hosts and it seems to kill the pCPU - I believe other VMs were impacted but will recheck.
2012-09-09 12:53 PM
I can understand from a ONTAP point of view why this was done, not giving the CPU halt instructions means more IOPS as it seems adding the additional CPU requests takes processing away from other things. This is how physical filers work so they've taken the same code.
Unfortunately this just isn't going to cut it in a production environment. ONTAP Edge is for remote offices and production workloads, probably going to be running on a single ESXi host without shared storage. A typical branch office server may have 2 CPUs with 4 cores per CPU. This means the VSA will be using a quarter of all resources available on the host and without remote physical shared storage and being only on a single host, there will be no vMotion or DRS to move it anywhere which will dramatically reduce the capacity of the host for other VMs.
So, you may land up having to purchase additional ESXi hosts.
Still think the VSA is a fantastic step forward but we see how difficult it can be to move things from the physical world especially with appliances where you assume complete control of your physical device to the virtual world where sharing is caring.
Hopefuly the boffins at NetApp are working on this and can silently insert those CPU halt instructions without affecting IOPS or find another way but currently this is certainly an issue.