KVM for IBM z Systems Limits and Configuration Recommendations

Transcription

1 KVM for IBM z Systems KVM for IBM z Systems Limits and Configuration Recommendations This document can be found on the web, Search for document number under the category of White Papers. Version Date: October 28, 2016 KVM for IBM z Systems Team

2 Special Notices Please Note: Any performance data contained herein was determined in a controlled environment. Therefore, the results obtained in other operating environments may vary significantly. Some measurements may have been made on development-level systems and there is no guarantee that these measurements will be the same on generally available systems. Furthermore, some measurements may have been estimated through extrapolation. Actual results may vary. Trademarks IBM, IBM logo, LinuxONE Emperor, LinuxONE Rockhopper, and z Systems are trademarks or registered trademarks of the International Business Machines Corporation. Adobe, the Adobe logo, PostScript, and the PostScript logo are either registered trademarks or trademarks of Adobe Systems Incorporated in the United States, and/or other countries. Cell Broadband Engine is a trademark of Sony Computer Entertainment, Inc. in the United States, other countries, or both and is used under license therefrom. InfiniBand and InfiniBand Trade Association are registered trademarks of the InfiniBand Trade Association. Intel, Intel logo, Intel Inside, Intel Inside logo, Intel Centrino, Intel Centrino logo, Celeron, Intel Xeon, Intel SpeedStep, Itanium, and Pentium are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries. Java and all Java-based trademarks are trademarks of Sun Microsystems, Inc. in the United States, other countries, or both. Linux is a registered trademark of Linus Torvalds in the United States, other countries, or both. Microsoft, Windows, Windows NT, and the Windows logo are trademarks of Microsoft Corporation in the United States, other countries, or both. OpenStack is a trademark of OpenStack LLC. The OpenStack trademark policy is available on the OpenStack website. TEALEAF is a registered trademark of Tealeaf, an IBM Company. UNIX is a registered trademark of The Open Group in the United States and other countries. Worklight is a trademark or registered trademark of Worklight, an IBM Company. All statements regarding IBM s future direction and intent are subject to change or withdrawal without notice, and represent goals and objectives only. This document is current as of the initial date of publication and may be changed by IBM at any time. Not all offerings are available in every country in which IBM operates.it is the user s responsibility to evaluate and verify the operation of any other products or programs with IBM products and programs. THE INFORMATION IN THIS DOCUMENT IS PROVIDED AS IS WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED, INCLUDING WITHOUT ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND ANY WARRANTY OR CONDITION OF NON-INFRINGEMENT. IBM products are warranted according to the terms and conditions of the agreements under which they are provided.

3 Table of Contents Introduction...4 Limits Table...5 Discussion...6 Web location of document ( 3

4 Introduction The following table summarizes recommended and maximum limits for KVM for IBM z Systems Following the table you will find additional information about each category. Terminology used in the table below. Recommended Limit: A configuration that is inside defined limits that will be covered by a support statement in terms of functional and performance issues. Maximum Limit: A configuration that is inside defined limits that will be covered by a support statement in terms of functional issues. Note: a customer may define configurations outside these limits, however, such configurations will not be supported. Web location of document ( 4

5 Limits Table Category Function Recommended Limit Maximum Limit CPU Overcommit 10:1 N/A Host CPUs 101 (zec12) z13: (1 drawer) 141 (z13) Per Guest vcpus Guest vcpus <= Host CPUs 64 Memory Overcommit 2:1 N/A Maximum Host 1 TB (zec12, z13) 1 TB (zec12) 8 TB (z13) Networking OSA CHPIDs per Host 16 N/A Virtual NICs per Host (with OpenVswitch) Virtual NICs per Guest 8 32 Storage Total attached zfcp LUNs K Total attached ECKD Devices K Virtual Block Disks per Host K Virtual Block Disks per Guest HPM Guests per Service Class Service Classes per Host Other Guests per Host Web location of document ( 5

6 Discussion Each of the categories listed above are discussed in the paragraphs below. CPU The 10:1 vcpu:cpu overcommit ratio was tested with the J2EE Daytrader 3.0 application running on several KVM guests. All guests were running at an equivalent and constant throughput. The effect on guest and overall host performance when overcommitting resources varies greatly and can either show little effect or significant effect. Careful selection of the combination of guest workloads that run on an overcommitted host can help to ease the performance effects. Memory The 2:1 memory overcommit ratio was tested with the J2EE Daytrader 3.0 application running on several KVM guests. All guests were running at an equivalent and constant throughput. The effect on guest and overall host performance when overcommitting resources varies greatly and can either show little effect or significant effect. Careful selection of the combination of guest workloads that run on an overcommitted host can help to ease the performance effects. Networking 1. The network throughput between two LPARs is about half of the expected level when both LPARs are using the same OSA device, when compared to the case where each LPAR uses different OSA devices. 2. Due to a OSA capacity restriction, only 1000 Virtual Servers using MacVTap can be started simultaneously per OSA card 3. The command ifconfig is obsolete. Please use ip addr ip link ip s link 4. In case the customer needs to modify the buffer count value for each network adapter, without a reboot, the customer must use the following recommended procedure: ip link set eth0 down && echo 0 > /sys/devices/qeth/0.0.f5f0/online && echo 64 > /sys/devices/qeth0.0.f5f0/buffer_count && echo 1 > /sys/devices/qeth/0.0.f5f0/online && ip link set eth0 up 5. When a guest is configured to use an ethernet bridge (such as virbr0) using something like the xml fragment below: Web location of document ( 6

7 <interface type= bridge > <mac address= 00:06:fe:10:35:01 /> <source bridge= virbr0/> <target dev= net001 /> <model type= virtio /> <alias name= net0 /> <address type= ccw cssid= 0xfe ssid= 0x0 devno= 0x0002 /> </interface> The net001 device created by qemu has a default txqueuelen of 500. If the txqueuelen is modified on the hypervisor to 2500 a significant increase in network performance occurs. We suggest setting txqueuelen=2500 and buffercnt=128. Storage If you wish to access more than 511 scsi luns on a host, you need to add the following kernel parameters to /etc/zipl.conf, and run zipl: scsi_mod.max_luns=2000 scsi_mod.max_report_lunx=1999 Web location of document ( 7

8 HPM The total number of workloads could vary depending on the partition of service classes. Other The maximum number of concurrent live guest migrations based on the default configuration - is 32. Web location of document ( 8