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Certification of Xen on Linux / Itanium

 
Every certification takes some time. You might ask why the LinuxLab Xen Itanium certification for SAP took so long. It’s due to the fact, that we applied the same comprehensive rules on the Xen on Itanium certification as we did during the LinuxLab Virtualization Certification Workshop on VMware and Xen on x86_64.  
 

Goals

 

  • Technical certification of the Itanium Processor 9040
  • Technical certification of RHEL5.1 Xen on IA64
  • Examine the impact on SAP application level having 150% resource allocation (CPU)

 

Hardware

 

  • HP rx3600 dual socket dual core Itanium CPU with 1,60Ghz, 32GB RAM, 4x internal disks (RAID5) attached to an MSA1000 (?) storage via a single QLogic ISP2422-based with 1x4Gbit, sec

 

Software

 

  • RHEL5.1 including all online updates

 

Test Setup

 
The test machine has 4 CPU cores and 32GB of memory. The slicing was done to fulfill at least the 50%, 100% and 150% test case. The certification on the commodity hardware had a more detailed slicing because of more available cores. The same kind of slicing for the currently used 4 core machine means that a virtual machine has just one single virtual CPU. Such a setup is not feasible for SAP Software which normally uses more then one core. The 50%, 100% and 150% slicing of the Itanium machine means, one virtual machine has 2 virtual CPUs (corresponding to two physical cores) and 8GB of memory. The storage exposes a 1TB device to domain 0. For every virtual machine a logical volume of 150GB is available on the 1TB device leaving 550GB untouched. Please note, that all virtual machines are sharing the same physical disks which could lead to a performance challenge during the I/O tests.
 
Having three virtual machines of this kind allows us to examine a 150% CPU allocation leaving 8GB memory for domain 0 for administrative tasks. The test cases in this setup follow the same rules as in the LinuxLab Virtualization Certification Workshop for the x86_64 platform. These are installing an SAP ERP2005SR1 system measuring the I/O capabilities followed by a memory throughput test case. Due to restricted resources, there was no possibility to perform the CPU scalability test.
 

Test procedure

 

  • Install the Xen Hypervisor
  • Install three virtual machines
  • Perform Tests in one VM (50% host utilization)
  • Perform Tests in two VM’s (100% host utilization)
  • Perform Tests in three VM’s (150% host utilization)

 

Results

 
After all tests finished successfully, the results look very promising. The I/O tests perform very promising although the same disks were used. The memory scalability test clearly shows, that virtualization on IA64 perform extremely well. The following table gives you the throughput of a single VM in the three test cases. The first row (one VM running) is the base line having 100% throughput values for all tests. The second row, two VM’s are running, shows the full host utilization whereas the third row shows the throughput when three VM’s are running the tests.  
 

Compare Base  I/O write  I/O read/write  I/O read  Memory throughput 
 1 VM (50% host usage) 100% 100%  100% 100%
 2 VM’s (100% host usage) 46%  82%  96%  94% 
 3 VM’s (150% host usage) 33%  56%  80%  64% 

Certified Components

 

  • Software: RHEL 5.1 and later on Linux Itanium having RHEL 5.1 guests
  • Hardware: Any Itanium Server which is explicitly listed by the SAP LinuxLab Hardware Partners

 
The next step for the Xen Itanium certification is to look at several NUMA features having several nodes on physical hardware. The HP rx3600 machine only has one single NUMA node, which performs very well. The questions that arises is, what about the performance and scalability having more nodes available? The Hypervisor has to do a very tough job when scheduling the virtual machines on the nodes because of the local memory. I’m looking forward to get my hands on such a machine to do such a certification. If you have any questions or recommendations, please use the comment function of the blog or email me directly. My address details are available through my SDN business card.

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