Dell Storage PS Series Arrays: Scalability and Growth in Virtual Environments Dell EMC Engineering January 2017 A Dell EMC Technical White Paper
Revisions Date Description November 2011 Initial release January 2017 Updated to reflect new branding and formatting Acknowledgements Engineering: Chuck Armstrong The information in this publication is provided “as is.” Dell Inc. makes no representations or warranties of any kind with respect to the information in this publication, and specifically disclaims implied warranties of merchantability or fitness for a particular purpose.
Table of contents 1 Introduction ...................................................................................................................................................................5 2 Virtual, hypervisor-based environments .......................................................................................................................6 3 Larger volumes ..................................................................................................................................
Executive summary This document provides VMware® and Dell™ PS Series storage administrators with recommended best practices when configuring a virtual environment. This paper covers Dell recommendations on how to plan and scale virtual environments with PS Series arrays, specifically with regard to making connections to PS Series volumes and managing connection counts to a PS Series Group. This paper also covers connectivity and high availability as well as some common performance-tuning best practices.
1 Introduction The PS Series SAN architecture allows for mobility of storage volumes across the peer storage arrays. This architecture also includes a Network Load Balancer (NLB) to redirect iSCSI login sessions to provide better efficiency and bandwidth management to the SAN.
2 Virtual, hypervisor-based environments Virtualization adds a new set of planning and scaling challenges to the data center. For example, the advanced virtual machine availability features in VMware, such as High Availability, Distributed Resource Scheduling, Fault Tolerance, and VMware vSphere® Storage vMotion®, depend on the ability of all the VMware ESXi™ hosts in a cluster to see all of the volumes. The same is true for Microsoft® Hyper-V® clusters utilizing Clustered Shared Volumes.
In larger environments, these additional MPIO connections need to be taken into account at design time and as the environment scales. Here is an example of how quickly connections can be consumed: Assume there is a 16 node cluster connecting to 20 volumes in a single storage pool with 3 PS arrays.
3 Larger volumes Another tactic for reducing volume connections in virtual environments is to create larger volumes and fewer of them. In many cases, administrators start with a particular volume size to host virtual machines, and as their environment grows, the tendency is to create more volumes of the same size instead of creating or growing larger volumes to handle additional growth. This process only works for so long, because eventually the volume connection count starts to add up.
4 CHAP authentication for access control Manipulating MPIO modules and increasing volume sizes are both great ways to manage volume connections but there are other best practices and recommendations that can also help control how connections are made to PS Series volumes. CHAP authentication for access control lists can be very beneficial. In fact, for larger cluster environments, CHAP is the preferred method of volume access authentication, from an ease-ofadministration point of view.
5 Group and pool transparency When it comes to scaling PS arrays, there are two trains of thought: scale up or scale out. The PS Series architecture uses a scale-out architecture, but there are times when scaling out is not enough. For example, customer A currently has 3 PS arrays and is purchasing 3 more. Looking at customer A’s storage group, they have 3 arrays and 50 volumes deployed in a single storage pool.
6 VMware pods Creating VMware pods can help minimize connections in large VMware environments. The notion of VMware pods simply refers to reducing the number of nodes from large (many node) clusters to smaller clusters that are managed in the overall VMware vCenter® datacenter hierarchy. This allows for the continuation of HA/DRS and also allows better manageability of the volume connection count.
7 Data protection and business continuity Another important discussion point is data protection and business continuity. PS Series snapshots are done at the volume level, and in most cases, snapshots will not affect storage group connections if they are used to roll back the parent volume to a particular point in time. However, it is not uncommon to use snapshots as side-by-side copies in which the host connects directly to the snapshot instead of recovering the parent volume with a rollback operation.
8 Replication and scale It is important to understand how replication plays into the connection-count limitations and design of a DR site. PS Series firmware allows replication reserve space to be selected from a single pool at the destination site. Recovery operations must be planned accordingly because any or all volume(s) from any pool in Site A can be replicated to Site B, but there must be enough replication reserve in the pool designated at Site B to accommodate replication activities from Site A.
9 Summary With virtualized data center environments being the standard, it is important that administrators understand exactly how to manage and control growth and sprawl of resources. Managing multipath configurations, larger volume sizes, CHAP authentication, utilizing group and storage pool transparency, and distributing cluster environments are all ways to scale and manage connections to PS Series SANs for virtualized environments.
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