High transaction Websites challenge storage admins: businesses turning from DAS to SAN.

Busy, high-transaction websites present a distinct challenge to storage administrators. These types of sites may be large portals, corporate Intranets, busy ecommerce sites, online service providers or Web-based application services. They have two things in common: complex infrastructures made up of Web servers, application servers, domain and firewall servers, and massive data storage; and the requirement to maintain high performance and high availability of applications and data.

Configurations differ according to the nature of the website, but common elements include front-end clustered servers called a Web farm, mid-tier application and database servers, and storage devices. For example, an ecommerce website would have a front-end Web farm serving up HTML pages with relatively static information. Mid-tier application and database hosts serve updated and customized content to the browsers, while data is backed up to storage devices. Storage and availability requirements change with different configurations: front-end clusters demand high performance and generous bandwidth, and run clustering software that allows for immediate server replacement without service interruption. Backups protect the HTML content but are not critical, since the Web farms do not generally host dynamic data. The application servers are a different matter. Their data is often sensitive, time-sensitive and often regulated, and storage administrators must make certain that this data is protected and highly avai lable. Application servers are not always mid-tier, since they can also be the front-end servers in a Web services/application delivery environment. In this case, performance and availability are absolutely crucial to keep applications available to subscribers.

Web services are a particular challenge to data availability. Some vendors broadly define Web services as a service or application that can run over the Internet, but the accepted definition is a bit more complicated. Essentially, Web services are collections of software components that react to incoming requests from a variety of sources, and deliver data and services in response to those requests. Web services use Internet coding standards such as XML to assign common names to stored data and incoming requests. Web services are, by nature, dynamic and must operate real-time so that generated data can move quickly and be immediately available. This requires protected and redundant data storage, but developers have paid scant attention to data protection needs. Yet according to the Hurwitz Group, storage management for the growing Web services market is critical and requires backup, event management, recovery, and alternate data path routing services. This is particularly important in hosted applications, whe re trust between client and host is imperative.

High transaction Web models can present different needs and challenges:

1. Service provider Citrix delivers applications by acting as a liaison between the client and application hosts. In this case, client browsers lock onto a Web server address that is pointed to the Citrix server. Citrix sets up a session where the client's browser talks to another party's server while accessing data from several different locations. Citrix must protect its servers and connections, but does not have significant data stores.

2. An ecommerce site runs an Oracle database through its Web server. Server clusters sit on the site's front-end, grabbing dynamic data and application processing from backend database servers. A SAN backs up and replicates data from both Web farm and application servers, and IT runs different protection schemes by application priority. The Web farm static pages are backed up nightly. Since the pages are duplicated among the cluster, backup does not impact performance. Since the data from the application servers is critical, IT uses snapshots, runs online backups onto secondary disk, and replicates data to a remote site.

3. Hosting company USi uses a three-tier model for its website. The top tier is a communications layer with redundant routers and switches, as well as multi-vendor carriers and telecom devices. Clients may run hosted applications through VPNs or the Web. The second tier consists of separate server clusters for individual clients, and the third tier is shared networked storage. A typical installation for a large publishing client included EMC storage, Sun servers, Oracle and Quest databases, VPNs and storage management replication software. The site also maintains an alternative backup site.

Whatever the storage model, Comm Vault's director o f marketing Chris Van Waggoner lists two distinct IT management issues in demanding Web environments:

* Front-end: keep the site running. IT maintains Web farm networks by load balancing, managing clusters, protecting Web access, and related tasks. In this case there are many individual servers that generally look identical from an installed software perspective: they all use a single operating system and identical software, and are capable of serving up identical views should one server go down. The Web farm must maintain a high rate of speed to quickly deliver Internet pages, so the goal in the front-end is to swap out downed servers without interrupting Web page viewing.

* Back-end: protect the data. The back-end servers are driven by databases and applications like financial and CRM software. These applications are continuously processing and returning data to the Web server front line. A classic example is Amazon.com, which keeps data on customer identities, preferences and buying patterns. More importantly, they also maintain huge data stores on orders and fufflllment and must protect this data. The main goal in the backend is to protect the data from intrusion or damage.

Websites and Storage

There are different storage models based on DAS, NAS or SAN. Each one can be ideal for a given environment, and IT often combines them to meet different needs.

DAS

For all the publicity and advantages of SANs, direct-attached storage remains a viable alternative in certain environments. Mike Adams, senior product marketing manager at Veritas, said, "NAS and SAN have been key architectures over the past few years. But one of the other popular configurations I've seen deployed is direct-attached storage as well. On these Web farms, you may have a direct Fibre or SCSI attachment to a large tape library or a large disk farm. You don't have to take advantage of NAS or SAN, but can also do a direct-attached model."

Many high-transaction Websites still use direct-attached storage, which has historically been the cheapest form of storage and the easiest to deploy, as many servers come with their own bundled storage. However, the costs of managing DAS in large server environments can be prohibitive. Management costs. grow significantly over time, since the more DAS a company must manage the heavier the burden on IT staff. Powerful management tools do exist in DAS environments, such as cluster management software that can failover server processes and storage to a secondary server. But in general, SANs offer multiple path capabilities and redundant architectures that do not require as much manual intervention as DAS.

NAS

NAS installations in high-transaction Web environments require robust, integrated and scalable filers. These environments tend to present large amounts of static information on the front-end, since these models benefit the most from file-based serving. NAS storage systems also handle data sharing between Web server engines and can initiate server-less backup and replication, which offloads processing cycles from the servers. Storage should meet the same high level of performance as the servers do, according to Keith Brown, Network Appliance's director of technology and strategy. "Performance is key in the servers and is also key in the storage space. The high performance requirement in storage is one of the elements that make business quite challenging."

Low-end and most midrange NAS appliances cannot support high transaction websites, but large NAS filers can provide good storage management as well as file sharing capabilities. Brown stressed the integrated storage services that robust NAS devices can offer. He said, "Web service infrastructure and portals can become very complex because of the structure of the Web applications. How data is exchanged between these systems usually involves databases, so you've got database functionality to worry about. They end up being very sophisticated systems with a high level of complexity. I'd argue that the last thing you need on top of that is storage system complexity. The simpler you can make the infrastructure that supports the complex application, the better it will be for you and the more cost-effectively you can employ the portal."

A growing number of Web data centers combine NAS and SAN using NAS gateways. This allows them to gain the advantages of block and file level serving and sharing.

SAN

Lesley Taufer, president of Boulder Corporation, reports that many Web businesses are turning away from DAS to SAN. "In large organizations, more and more of them are looking at SANs as the most secure storage and most able to deliver the redundancy you might need." This is not only due to dropping prices on storage area network components, but also to the compelling ROI that a well-planned SAN can offer. Even expensive equipment can present an excellent return on investment. For example, Taufer said, "Tape libraries are starting to be a standard, as opposed to a tape unit capable of doing one or two tapes, especially in large storage areas. Even some of the really monster libraries are starting to look economical to people."

SANs offer redundancy and protection capabilities in Web environments that DAS does not always offer. Technologies like snapshots and shadow caching, where backup routines use fast cache memory to backup online data, allow storage administrators to backup active datasets without taking them offline. According to Taufer, moving to SAN from DAS allows IT to run backups without loss of performance, to cluster with different operating systems, and to establish redundancy and fault tolerance.

"No size fits all" is true in high-transaction Web environments, where different configurations and data types need multiple levels of data protection and availability. Companies and their integrators need to match data protection to application needs and priorities, and to assign storage schemes accordingly.

www.veritas.com

www.boulder.com

www.netapp.com

www.commvault.com