Best Practices for Sharing an iSCSI SAN Infrastructure with Dell PS Series and SC Series Storage using VMware vSphere Hosts Dell Storage Engineering January 2017 Dell EMC Best Practices
Revisions Date Description March 2015 Initial release April 2015 Added specific iSCSI NIC optimization settings for shared host October 2015 Updated for VMware ESXi 6.0 and added dedicated host information January 2017 Updated for VMware ESXi 6.5 Acknowledgements This paper was produced by the following members of the Dell Storage team: Engineering: Chuck Armstrong Editing: Camille Daily The information in this publication is provided “as is.” Dell Inc.
Table of contents Revisions.............................................................................................................................................................................2 Acknowledgements .............................................................................................................................................................2 1 2 3 Introduction ................................................................................................................
6.1 Test environment ..............................................................................................................................................26 6.2 I/O performance testing ....................................................................................................................................26 6.2.1 I/O performance results and analysis: shared hosts ........................................................................................26 6.2.
1 Introduction Dell™ PS Series and Dell EMC™ SC Series storage systems both support storage area networks (SANs) over the iSCSI protocol.
1.3 Terminology The following terms are used throughout this document: Converged network adapter (CNA): A network adapter that supports convergence of simultaneous communication of both traditional Ethernet and TCP/IP protocols as well as storage networking protocols such as internet SCSI (iSCSI) or Fibre Channel over Ethernet (FCoE) using the same physical network interface port. Data Center Bridging (DCB): A set of enhancements made to the IEEE 802.
Network interface card (NIC): A network interface card or network interface controller is an expansion board inserted into the computer/server so that the computer/server can connect to a network. Most NICs are designed for a particular type of network (typically Ethernet) protocol (typically TCP/IP) and media.
2 Storage product overview The following sections provide an overview of the Dell storage products and technologies presented in this paper. 2.1 PS Series storage PS Series arrays deliver the benefits of consolidated networked storage in a self-managing iSCSI SAN that is affordable and easy to use, regardless of scale.
3 PS Series and SC Series iSCSI SAN coexistence PS Series and SC Series arrays can coexist in a shared iSCSI SAN, either with shared hosts or dedicated hosts. Shared hosts not only share the iSCSI SAN infrastructure, but also connect to storage targets on both the PS Series and SC Series arrays. Shared-host coexistence (see Figure 1) shares the iSCSI SAN infrastructure and has all hosts connected to both array platforms.
3.2 Topology of a shared iSCSI SAN infrastructure with dedicated hosts Shared iSCSI SAN with dedicated hosts reference topology 3.3 PS Series specific settings The use cases defined in this paper consist of SC Series arrays and connected VMware vSphere hosts sharing only the Ethernet iSCSI SAN infrastructure with existing PS Series storage and its connected hosts (dedicated), as well as SC Series arrays sharing not only the iSCSI SAN infrastructure, but also the VMware vSphere hosts (shared).
Note: Additional PS Series-specific information can be found in ESXi Versions 5.1, 5.5, or 6.0 Host Configuration Guide and Dell PS Series Configuration Guide. 3.4 SC Series specific settings A typical SC Series iSCSI implementation involves two separate, dedicated Ethernet fabrics as two fault domains with an independent IP subnet and unique, non-default VLANs in each switch fabric.
Figure 3 depicts proper connection from each host port to the SC Series storage ports within the same fault domain without traversing the switch interconnection. Connecting the host to SC Series ports Note: With the approach discussed in this paper, misconfiguration of the SC Series connectivity (for example, host ports not connected to the correct fault domain) can lead to loss of volume access in the event of a switch failure.
4 Enabling vSphere 6.5 host access to PS Series and SC Series iSCSI storage – shared This section assumes the environment is historically a PS Series storage environment and SC Series storage is being implemented into the existing environment, as shown in section 3.1 4.1 Configure access to PS Series storage This section covers configuring access to PS Series storage through the installation and assumes VMware licensing is Enterprise or Enterprise Plus and supports the use of MEM. 4.1.
4.2.2 Configuring the VMware iSCSI software initiator to access SC Series volumes For SC Series storage, the discovery portal addresses must be added manually to the dynamic discovery tab in the VMware iSCSI software initiator. SC Series storage presents front-end target ports and each volume is presented as a unique LUN. Redundant connections are made by creating multiple sessions with each of the virtual iSCSI target ports the array. For the purpose of this discussion, 10.10.10.35 and 10.10.10.
3. Right-click the iSCSI Software Adapter and click Rescan to connect to the targets. Note: This approach with VMware does not provide a way to restrict initiators to connect only to targets on the same fault domain. After preparing the vSphere host, create a server or cluster object in Dell Storage Manager and map volumes. Note: See the Create a Cluster Object in Enterprise Manager and Creating and mapping a volume in Enterprise Manager videos for additional information.
4.2.3 VMware native multipathing VMware provides native multipathing that can be used with any storage platform, if a vendor-provided multipath solution is not available. 4.2.4 Setting Path Selection Policy and storage performance settings - PS Series In a shared environment, where VMware hosts connect to both PS Series and SC Series storage targets, the multipath and iSCSI settings optimized by the MEM (described previously) for all PS Series volumes. Therefore, no modifications are required 4.2.
5 Enabling vSphere 6.5 host access to PS Series and SC Series iSCSI storage – dedicated This section assumes the environment is historically a PS Series storage environment and SC Series storage with new hosts dedicated to the SC Series storage is being introduced into the environment, where only the iSCSI SAN infrastructure is being shared, as shown in section 3.2 5.
1. From the VMware ESXi Web GUI (local host management utility that has replaced the C-Sharp client), select Networking, Virtual switches, and click Add standard virtual switch. 2. Click on Add uplink to add the second uplink. Input the vSwitch Name (iSCSI), the MTU (9000), select the appropriate vmnics in both Uplink 1 and Uplink 2, and click Add. 3. From Networking, select VMKernel NICs and click Add VMKernel NIC. 4.
5. Repeat steps 3-4 for the second VMKernel NIC (Shown completed). Note: The use of port binding when multiple vmnic uplinks exist on the vSwitch, all but one uplink must be placed in an unused state for each VMKernel port group. 6. Expand Networking, select the VMKernel port group (iSCSI-01), and click Edit settings.
7. When the ability to mark an adapter as unused becomes available, select Yes for Override failover order, select the vmnic to mark as unused, and click the Unused (currently not an available option).
Note: At the time of this writing, the local vSphere host GUI, the new web-based utility that has replaced the C-Sharp client, does not have the ability to set the secondary vmnic to unused for the kernel port group. This can be accomplished either using the vCenter Web GUI, or a command line utility. 8. Repeat steps 6-7 for the second VMKernel port group (iSCSI-02).
10. In the iSCSI enabled, click Enabled and click Add port binding in the Network port bindings section. 11. Select the first iSCSI VMKernel Portgroup and click Select. Repeat steps 10 and 11 for the second VMKernel Portgroup.
12. In the Dynamic targets section, click Add dynamic target twice, enter the two SC Series iSCSI target addresses, and click Save configuration. 13. Right-click the iSCSI Software Adapter and click Rescan to connect to the targets. Note: This approach with VMware does not provide a way to restrict initiators to connect only to targets on the same fault domain. After preparing the vSphere host, create a server or cluster object in Dell Storage manager and map volumes.
5.2.2 VMware native multipathing VMware provides native multipathing that can be used with any storage platform, if a vendor-provided multipath solution is not available. 5.2.3 Setting Path Selection Policy and storage performance settings - SC Series VMware hosts connected to the SC Series storage platform must use VMware’s native multipathing for SC Series volumes. Setting the Path Selection Policy (PSP) can be performed using either the vCenter GUI or a command line utility.
6 Test methodology Note: The test methodology used in this paper is only valid in the presented topology, components, and test cases. The results may not be directly applicable to environments with other components or variables. Additionally, the updated versions of vSphere, PS Series firmware, and SC Series SCOS show no indications of presenting different performance than that of previous versions. As such, the performance testing reflects the previous version of this document.
IOPS, latency measured in milliseconds (ms), throughput measured in megabytes per second (MBPS), retransmits (an indicator of network congestion), and other statistics (such as switch packet drops, discards, and pause frames) were collected from host, switch, and storage ports. These parameters were carefully analyzed to ensure that the host and iSCSI SAN network performance were not adversely impacted with both PS Series and SC Series storage being accessed simultaneously. 6.
140% 104% 120% 102% 100% 100% 80% 98% 60% 96% 40% 94% 20% 92% 0% Latency (ms) IOPS The following figures show the baseline IOPS and latency information gathered on the PS Series environment and how it compares after the introduction of the SC Series storage to the environment. Figure 4 and Figure 5 show the baseline information on the left and the shared environment data on the right, as a percentage of the baseline.
6.2.2 I/O performance results and analysis: dedicated hosts Performance analysis in the dedicated host environment is designed to show the impact to the PS Series storage environment when a dedicated SC Series storage environment is added to the same iSCSI infrastructure. Figure 6 below shows the baseline IOPS and latency information gathered on the PS Series environment on the left side.
Both VMs started running a vdbench 256K Write workload. Roughly midpoint in the hour-long test, one of the two iSCSI switches were powered off, simulating a switch failure. The output chart in Figure 7 shows a drop in IOPS and a spike in latency at the time of the failure, as would be expected. Also, as expected, the latency quickly recovers to roughly double the latency observed prior to the failure.
7 Best practice recommendations Always check the Dell Storage Compatibility Matrix to ensure that SAN components (such as switches and host NICs) are supported for both PS and SC Series deployments. For full support, the switches used for array connectivity must be validated for use with each solution individually. 7.1 Switch fabric Place all storage interfaces (including storage controller ports and host ports) in the default (native) VLAN when the iSCSI SAN infrastructure is shared.
8 Conclusion As a result of testing and analysis shown in this document, introducing SC Series storage into an existing PS Series storage iSCSI environment, whether in a dedicated or shared host configuration, will not significantly affect the performance of the PS Series storage. Understanding the effects of a coexisting storage environment is key to enabling future growth and expansion of existing PS Series environments.
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http://en.community.dell.com/techcenter/storage/w/wiki/4250.switch-configuration-guides-forEqualLogic-or-compellent-sans.aspx VMware ESXi 5.1, 5.5, or 6.0 Host Configuration: http://en.community.dell.
