SAP Note

Header Data

Symptom

You want to run SAP on Linux in a Citrix XenServer virtual machine.

Other Terms

Citrix, Citrix XenServerServer, Citrix XenServer, Linux, Red Hat, RHEL, SUSE, SLES, paravirtualization, para-virtualization, PV, virtualization, HVM

Reason and Prerequisites

Citrix XenServer is a virtualization product that enables the execution of multiple guest operating systems on the same computer hardware. Running SAP on Linux inside a virtual machine offers flexibility and may help you to reduce your TCO.

Solution

1. General information

Since November 29, 2010 SAP does support running SAP on Linux inside a Citrix XenServer virtual machine. You have to enable the vhostmd based monitoring for XenServer as described in SAP note 1532458; this is necessary to run in an SAP supported environment. The Linux distributions which can be used for Citrix XenServer virtualization are those that are Novell Yes! Certified. At the time of this writing, this includes SUSE Linux Enterprise Server 10 SP2 (SLES10 SP2) and SUSE Linux Enterprise Server 11 (SLES11). Later releases are supported as well. Please read the relevant installation notes on how to install those Linux distributions with Citrix XenServer. Running SAP products on Red Hat Enterprise Linux inside a virtual machine in Citrix XenServer is currently not supported. Although SAP solutions (including SAP NetWeaver and the SAP MaxDB database) are fully supported running inside a Citrix XenServer virtual machine, some database vendors might have different support statements when running in a virtualized environment. Please read SAP note 1122387 for more information on the support process for SAP with Citrix XenServer.

2. SAP guidelines for Citrix XenServer virtual machines

l Virtualization Method

           Currently only para-virtualization is supported. Fully virtualized machines might be supported in the future.

l Environment

           The host system (dom0) is running a minimalist Linux which is modified for high security and good performance. Citrix XenServer is able to run different operating systems as virtual machines (domU). However, if a distributor has support statements in place, which state that a certain combination is supported, e.g. a new hypervisor with an already certified guest system, then SAP will not deny the support of SAP components on this stack. Please be aware that this will not cover third party products (e.g. databases) as stated above.

l Update Strategy

           Citrix Systems will provide all necessary updates / patches for the Citrix XenServer Platform. Updates and patches for the individual Guest Operating System (domU) will be provided by the guest operating system vendor.

l Virtual resources

    1519590 - Virtualization with Citrix XenServer  

Version   3     Validity: 29.11.2010 - active   Language   English (Master)

Released On 29.11.2010 12:07:52

Release Status Released for Customer

Component XX-PART-CTX-XEN XenServer by Citrix

BC-OP-LNX Linux

Priority Recommendations / Additional Info

Category Installation information

Other Components

           Testing has shown that the performance overhead of the Citrix XenServer virtualization layer with the above mentioned distributions can be less than 5% compared to the native performance. Depending on the workload it is often even less. You may also use bigger configurations, although they haven't been tested by SAP.            Due to scalability reasons it's strongly recommended to run latest SLES releases, since performance of previous Linux distributions like SLES10 and SLES10 SP1 with SAP and more than 2 virtual CPUs per virtual machine was not optimal.            The host system (domain 0) memory usage will scale accordingly to the amount of virtual machines running on the Citrix XenServer. The dynamic memory management provides a high level of flexibility.

l Resource Over-subscription

           Citrix XenServer allows an over-subscription of available CPUs. SAP successfully ran performance tests in virtual machines (utilizing all available virtual CPUs to 100%) which oversubscribed the host system up to 150%. The performance degradation inside the virtual machines was linear reciprocal to the over-subscription. You may exceed the 150% over-subscription, but keep in mind, that the performance of virtual machines in such a scenario is not guaranteed. In case of performance problems, SAP can demand you to shutdown or pause other running virtual machines to check if the over-subscription caused problems.

l Storage configuration

           SAP strongly advises to place Citrix XenServer virtual machines on a raw devices. This is possible with the Citrix Storage Link Technology. Do not use the default LVM based Storage Repository for a virtual machine. If you run an SAP database instance on such a LVM based virtual machine the I/O performance will drop dramatically compared to a raw setup.            We also advise you to use an external storage for the virtual machines when using a SAP database instance. For SAP application servers, local disks are sufficient.

l Certified Hardware

           You may only run your host system on hardware which is certified for Citrix XenServer environments. Please have a look at the release notes of the LinuxLab Hardware Partners and check which servers are certified for Citrix XenServer explicitly. A list of notes of the released and certified hardware of the LinuxLab Hardware Partners is available in the "Supported hardware" section of SAP Note 171356.

Validity

This document is not restricted to a software component or software component version

References

This document refers to:

SAP Notes

This document is referenced by:

SAP Notes (4)

1532458   Monitoring of SAP on Citrix XenServer

1122387   Linux: SAP Support in virtualized environments

171356   SAP software on Linux: General information

171356   SAP software on Linux: General information

1532458   Monitoring of SAP on Citrix XenServer

962334   Linux: SAP on SUSE Xen virtual machine

1122387   Linux: SAP Support in virtualized environments