Description of problem: RHEL 4 supports up to 64GB using the hugemem kernel. RHEL 5 does not ship the hugemem kernel and officially restricts support to systems of 16GB or less. However, kernel-PAE will install and run systems up to 64GB with no warning message that this is an invalid consiguration. Engineering's position is that customers wanting to run larger systems should migrate to x86_64 architecture. Though there are not a large number of x86 systems, the ones that do exist typically are from large customers and we are inhibiting them from migrating to RHEL5. Many can't easily migrate their applications to run on 64 bit or they don't own the proprietary application software. The intent of this bug is to resolve the migration roadblock that customers running x86 16-64GB systems will experience if they can not migrate their applications to 64 bit. For them, this is a regression from RHEL4.
From Amit at Dell: Attaching the sos report from a PE6950 with 64 GB RAM that is loaded with RHEL5 32-bit. kernel-PAE sees all 64GB.
Created attachment 150707 [details] sos -- Kernel-PAE.tar.bz2
This bugzilla has Keywords: Regression. Since no regressions are allowed between releases, it is also being proposed as a blocker for this release. Please resolve ASAP.
The problem here is that there is no warning that the customer is running an invalid configuration in RHEL5. The 2.6.18 kernel will boot and appears to run with memory as large as 64GB. In RHEL3 and RHEL44, you could boot a 24GB kernel but it would likely behave poorly and the kernel would not even boot at 32GB. The first time the customer is aware that a valid RHEL4 configuration (albeit using the hugemem kernel) is now invalid in RHEL5 is when he/she calls Support and they relate that >16GB is not supported in 32 bit mode on RHEL5. It is also not clear that all applications can run or are certified in 32 bit mode on a 64 bit OS for RHEL5. This could be a significant customer migration problem to RHEL5.
Development Management has reviewed and declined this request. You may appeal this decision by reopening this request.