Bug 1908875

Summary:	RHCOS Resource Requirements under KVM on System z
Product:	OpenShift Container Platform	Reporter:	Philip Chan <chanphil>
Component:	Documentation	Assignee:	Vikram Goyal <vigoyal>
Status:	CLOSED NOTABUG	QA Contact:	Xiaoli Tian <xtian>
Severity:	low	Docs Contact:	Vikram Goyal <vigoyal>
Priority:	unspecified
Version:	4.7	CC:	aos-bugs, bbreard, christian.lapolt, Holger.Wolf, imcleod, jligon, jokerman, krmoser, miabbott, nstielau, wvoesch
Target Milestone:	---
Target Release:	4.7.0
Hardware:	s390x
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-02-08 22:53:51 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1903544

Description Philip Chan 2020-12-17 18:46:19 UTC

Description of problem:
Using the OCP install guide's official recommended memory requirements, we found that when using 8GB memory for the OCP nodes may not be sufficient running under KVM.  The BOE and POK test teams have both experienced inconsistencies with the RHCOS when defining only 8GB of memory for any of the OCP nodes(bootstrap, masters, workers).  When we define a minimum of 16GB or more, the installs have a higher chance of succeeding.  We're in the process of testing the exact memory requirement.  More details will be added once we have these results to share. 

Version-Release number of selected component (if applicable):
All versions of 47.83 RHCOS builds installed on KVM guest

How reproducible:
Consistently

Steps to Reproduce:
1. Define only 8GB memory for any OCP node
2. Perform a RHCOS install on that node
3.

Actual results: At any part of the install, the KVM guest will stop.


Expected results: Successful installation of RHCOS


Additional info: The purpose of this bugzilla is for our documentation update. 
 We're investigating the minimum KVM requirements for OCP 4.7. The results of these will be documented under the OCP install guide for KVM.

Comment 1 Micah Abbott 2020-12-17 19:08:17 UTC

(In reply to Philip Chan from comment #0)

> Additional info: The purpose of this bugzilla is for our documentation
> update. 
>  We're investigating the minimum KVM requirements for OCP 4.7. The results
> of these will be documented under the OCP install guide for KVM.

Moving to docs component per this bit of info

Comment 2 Holger Wolf 2021-01-13 13:40:04 UTC

(In reply to Philip Chan from comment #0)
> Description of problem:
> Using the OCP install guide's official recommended memory requirements, we
> found that when using 8GB memory for the OCP nodes may not be sufficient
> running under KVM.  The BOE and POK test teams have both experienced
> inconsistencies with the RHCOS when defining only 8GB of memory for any of
> the OCP nodes(bootstrap, masters, workers).  When we define a minimum of
> 16GB or more, the installs have a higher chance of succeeding.  We're in the
> process of testing the exact memory requirement.  More details will be added
> once we have these results to share. 
> 
> Version-Release number of selected component (if applicable):
> All versions of 47.83 RHCOS builds installed on KVM guest
> 
> How reproducible:
> Consistently
> 
> Steps to Reproduce:
> 1. Define only 8GB memory for any OCP node
> 2. Perform a RHCOS install on that node
> 3.
> 
> Actual results: At any part of the install, the KVM guest will stop.
> 
> 
 
To me that is a bug, since we have a setup with the original setup on Z with a alternative hipervisor zVM. It is unclear to me, why KVM needs more resources and therfore driving higher costs at the Customer shop for exact the same setup?

Therefore I'm not convined that this is a doc bug, for now it should go to the release notes.

@Phil,

can we deliver some memory/monitor data of the KVM hipervisor / Bastion node what happends here?

Comment 3 Philip Chan 2021-02-03 22:24:21 UTC

For the OCP 4.7 Release, we have written the install documentation for KVM to create a .qcow2 image and then load the provided RHCOS .qcow2 as the disk.  We will not perform a RHCOS installation from scratch.  Having thoroughly tested this procedure over the past month, we have not encountered the memory restraints that I originally observed with older RHCOS builds.  Furthermore, Kyle has performed hundreds of tests as a side comparison (where we installed RHCOS) using the minimum memory requirements as documented and has also not seen the problem with the installation occur.  We should be able to close the bugzilla for now, and if this were to arise again, we can re-open.

Thanks,
-Phil