How To Make A Clustered Nash System Work For A Large Data Center

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1 Technology Insight Paper Coho Data s DataStream Clustered NAS System Bridging a Gap Between Webscale and Enterprise IT Storage By John Webster November, 2014 Enabling you to make the best technology decisions

2 Coho Data s DataStream Clustered NAS System 1

3 Coho Data s DataStream Clustered NAS System 2 Executive Summary Many enterprise IT administrators are currently in the process of transforming their data center infrastructures to reduce the overall cost of computing while emphasizing continuous services delivery. Oftentimes we see multiple objectives driving these transformations that include standing up a user- responsive, services delivery engine that can simultaneously support existing applications while delivering new mobile, social, and analytics applications. Another objective addresses reducing or at least limiting the overall cost of computing while increasing application agility by deploying applications on commodity infrastructure, using software to differentiate and add value. A deployment model that can be examined for relevance here is the one commonly practiced by organizations commonly referred to as webscalers Amazon, Facebook, Google, and Twitter for example who have been able to achieve great scale at relatively low cost per unit of compute. An aspect of this model is often referred to as software- defined where software is used to define the functionality and value of low- cost, commodity- priced hardware infrastructure. Here we look at Coho Data s DataStream clustered NAS system in light of the software- defined model to see if it can be used to yield some of the benefits of webscale computing while preserving production quality performance and continuous availability. Webscale vs. Traditional IT The data centers built and used by webscale companies like Facebook, Google and Twitter differ significantly from those common to traditional IT. Webscalers commonly build for homogeneity in systems. Platforms typically share a common management layer. Open Source software is a hallmark of the application stack and web- facing applications are commonly written in- house. Traditional enterprise IT data centers on the other hand host a relatively large number of applications predominantly written by commercial applications vendors running on a variety of different systems with different operating systems and serving many different organizational units. Underlying the design and build philosophy of webscale computing is cost efficiency. Webscalers aim for infrastructural economies of scale, management automation and simplicity, mass standardization, and centralized management control. Because traditional IT as evolved over a much greater time period than webscale, enterprise data centers don t have the ability to easily homogenize, automate and standardize their environments using open source and home- grown applications. They have to balance the maintenance of legacy applications with modernized application development. At the same time, they must respond to the needs of diverse user groups whose demands on IT increase with the advance of mobile device usage and cloud computing alternatives. Nevertheless, aspects of the webscale model do indeed have something to offer enterprise IT and cloud services providers. These include:

4 Coho Data s DataStream Clustered NAS System 3 Leverage of commodity infrastructure massively replicable deployment of low- cost hardware to reduce infrastructure cost and the use of software to define the function of commodity infrastructure 99.99% system uptime at scale high availability achieved through an ability to tolerate failure without impact to service level or availability Clustering for scale aggregation of hundreds to thousands of low cost servers into computational units In addition, webscalers have learned how to do all of the above and more in a business environment where increasing competitive pressure to offer more services to more users is the norm 1. Webscale-inspired Storage Systems and storage vendors are now beginning to offer solutions for enterprise IT and services providers that are inspired by web- scale storage models. These can provide administrators of both environments with the ability to: Leverage lower- cost commodity hardware and transform it into highly functional storage systems with software a process often called Software Defined Storage Use clustering of storage nodes to achieve performance at scale and fault tolerance Tolerate component failure while maintaining data integrity and availability Upgrade capacity and introduce new technology on an as needed basis without downtime or a refresh of the entire storage system. Here we briefly review Coho Data DataStream clustered NAS system as an example. Coho DataStream Coho Data s DataStream is a NAS system that has been initially designed for VMware environments with support for non- virtualized NFS storage coming in DataStream currently supports vsphere 5.1 or later releases and includes VAAI support. 1 For more information on webscale computing, see The Data Center as a Computer An Introduction to the Design of Warehouse- Scale Machines, an ebook by Barroso, Clidares, and Holzle.

5 Coho Data s DataStream Clustered NAS System 4 DataStream features a unique scale- out clustering architecture based on hybrid storage nodes (Flash + SATA disk) called MicroArrays and redundant programmable switches 2 for clustering, data placement, routing, and load balancing (see Figure 1 below). Figure 1. The Coho Data DataStream clustered NAS architecture. Storage management services such as virtualization of physical devices and data replication are performed by MicroArrays. DataStream clusters can support hundreds of MicroArrays and offer the ability to scale performance and capacity linearly and without the additional overhead seen in some clustering implementations. DataStream can be scaled to 20 nodes currently with greater numbers promised in future. The Hybrid MicroArray Flash plus Disk The DataStream storage cluster building block is a pair of MicroArrays that have a combination of Flash and disk for storage, CPU, and network connectivity. A MicroArray pair is configured with four PCIe Flash memory cards along with twelve high capacity (currently 4 TB SATA 7200 RPM) hard disk drives for a total of up to 54 TB raw/26 TB useable storage. 2 Coho Data uses the terminology Software Defined Networking (SDN) in describing the DataStream switch.

6 Coho Data s DataStream Clustered NAS System 5 Data Placement and Management MicroArray storage virtualization software manages the placement of data on PCIe Flash and HDDs transparently to optimize access to data. Two copies of data are stored on write. Knowledge of data placement is distributed across the cluster and replicated as well. For management, a web GUI is the primary interface. A CLI is also available along with standard features such as SMTP alerts and SNMP. Built- in analytics provide prescriptive guidance on the right mix of flash and disk for optimal performance and economics for each customer's unique application environment. Redundant Programmable Switches As can be seen in Figure 1 above, IP connectivity for application server access is made through the programmable 1 or 10 Gb/s Ethernet DataStream switches that provide a single IP address for data across the cluster of MicroArrays. Each MicroArray is attached to the redundant DataStream switches through two 1/10GigE ports. Component Failure Tolerance DataStream offers administrators the ability to hot- swap MicroArrays, disks, and power supplies within a MicroArray. For network fault tolerance, DataStream supports redundant network links and a multi- switch redundancy option. Automation of data redistribution when adding additional MicroArrays (discovered automatically) and upgrading individual MicroArrays is also supported. Data Protection and Disaster Recovery Internal data protection is achieved via: Redundant data distribution via synchronous object replication between MicroArrays Snapshots and snapshot scheduling With the release of version 2.0, DataStream also supports two- site disaster recovery using asynchronous replication. As an option, scheduled application- consistent snapshots can be asynchronously replicated between MicroArrays without distance limitation. 3 Replication is configurable on a per VM basis and is performed as a background task. Administrators can also control replication frequency during operational cycles on a per workload basis to respond to varying recovery time objective (RTO) requirements. Scheduled replication is directly integrated with VMware vsphere. 3 Coho Data literature states that there is no distance limitation for asynchronous replication between DataStream clusters. However, Coho Data has tested data replication between sites from 800 miles to nearly 8,000 miles apart (within North America and also between continents).

7 Coho Data s DataStream Clustered NAS System 6 Evaluator Group Assessment Coho Data has initially limited DataStream to NFS datastores in VMware environments. However, because virtualization is a bedrock cloud implementation requirement for both enterprise IT and service provider administrators, this limitation can still afford Coho Data more than ample opportunity to achieve a significant market presence as a clustered scale- out NAS vendor. DataStream s management simplicity and seamless scalability should be popular with IT VMware administrators and generalists alike. To go beyond the initial target, we believe that Coho Data will expand protocol offerings to include a full NFS implementation, Hadoop mounted device support, and a custom API for software development in future releases. DataStream offers both enterprise IT and service provider administrators an ability to inject webscale design concepts into their production storage environment. DataStream offers continuous availability under differing failure scenarios as expressed in support for hot swap MicroArrays, disks and power supplies. DataStream functionality is deliverable as software defined infrastructure. And MicroArray pairs support both Flash and rotating disk for performance and capacity at large scale. Coho Data has indeed developed an advanced clustered NAS system that offers some of the system capabilities that webscalers use to achieve continuous availability at scale while leveraging low- cost commodity hardware. About Evaluator Group Evaluator Group Inc. is a technology research and advisory company covering Information Management, Storage and Systems. Executives and IT Managers use us daily to make informed decisions to architect and purchase systems supporting their digital data. We get beyond the technology landscape by defining requirements and knowing the products in- depth along with the intricacies that dictate long- term successful strategies. Copyright 2014 Evaluator Group, Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or stored in a database or retrieval system for any purpose without the express written consent of Evaluator Group Inc. The information contained in this document is subject to change without notice. Evaluator Group assumes no responsibility for errors or omissions. Evaluator Group makes no expressed or implied warranties in this document relating to the use or operation of the products described herein. In no event shall Evaluator Group be liable for any indirect, special, inconsequential or incidental damages arising out of or associated with any aspect of this publication, even if advised of the possibility of such damages. The Evaluator Series is a trademark of Evaluator Group, Inc. All other trademarks are the property of their respective companies.