At $54,990, Volera's Velocity CDN (vCDN) solution costs significantly more than any of its competitors. Yet this solution's Excelerator cache server aced every test we threw at it and outperformed CacheFlow's and F5's solutions in the configuration, management and content-delivery categories thanks to its excellent System Controller and Content Controller devices. You get what you pay for.
VCDN is aimed at large enterprises and service providers. Volera says with one System Controller up to 20 administrators can manage more than 2,000 Excelerators. System Controller configures, manages and monitors Excelerators; Content Controller manages content distribution. A third element, Content Accountant--which we did not test--tracks, collects and exports usage information for both cache servers and content. But like CacheFlow's and F5's solutions, vCDN has usage logs that also work with third-party reporting and billing tools.
Excelerator came on a CD-ROM. Volera engineers do not recommend the use of RAID; instead, Excelerator uses a special disk OS optimized for caching, and using RAID with Excelerator may provide lower performance at a higher price. We reconfigured the server's four disks as four separate volumes without RAID, but we didn't remove the RAID chip from the Dell 2550. Our glitchless installation took about 20 minutes (visit Volera.com for information on the hardware platforms Volera supports).
The Excelerator console came up in a locked state but was easy to unlock and navigate with the CLI. As with the CLIs from CacheFlow and F5, a "?" brings up lists of available commands and options. Excelerator can be initialized using a GUI or a menu-based command line. The GUI has the look and feel of a Novell NetWare 5 installation. Either way, you input the IP schema, set the date and time and import the license from disk. From a Web browser, we enabled client acceleration and bound the proxy service to its IP address.
On our simulated T1 line, Excelerator saved up to 94 percent of bandwidth while delivering more than 2,000 hps. On the simulated T3, Excelerator's performance improved to more than 2,500 hps, also above the pack. It stayed on top when emulating busy LAN environments with 100-ms delay and 200-ms delay in both directions. All the while, Excelerator never exceeded 50 percent CPU utilization. That left plenty of headroom, even considering the Dell hardware's 1,000-MHz processors and 1,024 MB of RAM.
Excelerator uses 16 MB to 32 MB of RAM for the OS and devotes the rest to the Cache Object Store, Volera's proprietary file system.
Velocity CDN
Caching is mature technology, but the content-delivery portions of all the solutions we tested are barely past version 1.0. Therefore, it was difficult to come up with a shortlist of the features they should include. When Gartner looked at eCDNs' "content-management" aspect, it identified content diversity, content control and logging as selection criteria. We wanted more.
Our participants' content diversity is limited to cachable Web objects. This is not much of a differentiator when you review the protocols Volera, CacheFlow and F5 support. As for logging, each vendor provides detailed logs in standard formats but relies on third-party tools to make them useful (despite Volera's Content Accountant software for aggregating and analyzing logs).
Beyond Gartner's shortlist, we looked for a single point of access to view the entire delivery process from origin server to cache server. We also looked for control in identifying content, delivering it to cache servers, and what policies or attributes could apply to the object once it's in cache. Finally, we looked for job-control functions that detailed the entire process and provided status conditions. VCDN had it all.
VCDN's Java-based System Controller and Content Controller came on a Compaq DL 360 running Red Hat Linux 7.0, and provided the best single point of access for content delivery in our roundup. Although vCDN lacks an immediate way to test a connection with an origin server (F5's Global-Site Controller could do this), we got summary status information when content was not delivered on schedule. VCDN also provided the most detailed view and best configuration utility for the Excelerator.
In identifying and delivering original content, vCDN did the best job. Volera uses URL gets to obtain content and make up collections--the top level of content to deliver to cache servers. Because collections are separate from job control and delivery points, administrators can change items without affecting the other content-delivery jobs. VCDN's approach is more straightforward than that of CacheFlow's cIQ Director, which brings together content, calendars and actions under one umbrella.
VCDN provides attributes for each URL in a collection. These attributes control object collection and restrict access control while in cache. For example, you can collect other Web objects linked to a URL and dig to configurable levels or depths of a Web site. By default, the Controller will go one level deep to include the top page, graphics and text objects. You also can follow links to other hosts. To avoid downloading too much information, you can limit the amount of data you want from each URL. Once the URL and its associated objects are in cache, limits can be set on the number of concurrent connections. And, like F5's Global-Site Controller, vCDN lets you supply authentication information.
Each collection supports configurable monitoring and reporting parameters, a feature neither CacheFlow's nor F5's solution provides. Once you create the collection, you associate it with actions like prepopulate, pin, bypass or purge, and set a calendar for execution.
VCDN gives large enterprises their money's worth. The only item this solution lacked was an appliance; however, Volera licenses Excelerator to Compaq, Dell and IBM, which build dedicated TaskSmart Appliances, PowerApp.Cache Appliances and IBM eServer xSeries Servers, respectively.
Volera Velocity Content Distribution Network: Volera System Controller, Volera Content Controller, Volera Excelerator 2.1., (800) 219-1800, (408) 967-9000; www.volera.com or sales@volera.com
Cacheflow Security Gateway Appliance and cIQ Director
We installed and configured CacheFlow's eCDN solution with the greatest of ease, and received the most responsive content-delivery tool among the products we tested. Although it fell short on performance and lacked the extensive management capabilities of Volera's vCDN, it came at the lowest overall price: $22,990.
The Security Gateway Appliance will get you caching in no time. CacheFlow optimized its CacheOS version 5 prior to delivery as a forward-proxy cache. Like Volera's solution, CacheFlow devotes a minimal amount of physical RAM to its proprietary OS and reserves the rest (630 MB) for RAM cache.
The Security Gateway was the easiest to configure of the products we looked at. A joystick on the front panel of the appliance lets you set the IP schema. Although the joystick may not satisfy a die-hard gamer, we found it simple enough to use. From there, a Web browser accessed the device management console through default Port 8081.
Although the Security Gateway had 256 MB less available RAM than Volera's Excelerator, its performance rivaled that of Excelerator in the T1 and T3 simulations. CacheFlow's appliance provided a 94 percent bandwidth savings over our simulated T1 line, compared with Volera's 95 percent. When the pipe was increased to T3, CacheFlow's offering, like Volera's vCDN, showed a 99 percent bandwidth savings. The CacheFlow server lost ground in our latency tests when we introduced problems. This may be attributed to CacheFlow's configurable support for object pipelining.
Web browsers typically make numerous round-trips to and from origin servers in serial fashion to obtain all the Web objects needed to build a page. CacheFlow terminates the client connection at the SGA and opens up as many simultaneous TCP connections with the origin servers as possible to retrieve objects in parallel and deliver them to the client. This pipelining may be problematic if one of the requests were dropped or delayed. But Volera uses a similar algorithm in its operating system and did not suffer in the latency tests. Although the feature can be turned off, we left it in its default setting to remain comparable with Volera.
Security Gateway had a respectable price/efficiency rating of .12. With its low overall cost, the CacheFlow solution would be a good match for small and midsize enterprises that don't have the budgets for Volera's eCDN.
Serving It Up
The cIQ Director is the architecture CacheFlow's solution uses to distribute content to cache devices in the enterprise. Like our other participants, CacheFlow separates the content control and multiple device management from standalone caches. The cIQ Director sets user and content policies, manages multiple device configurations and distributes content to Security Gateway Appliances. The cIQ Director has a 450-MHz processor, 512 MB of RAM and 20 GB of disk storage. In our tests, the cIQ Director communicated via SSH with a Java application (JRE version 1.3.1_02) running under Microsoft Windows 2000. CacheFlow says future versions will run directly from the appliance, though we had no complaints about the current version's snappy performance.
Like vCDN, the cIQ Director provides a single point of access to the content-delivery process. We set up a domain and created a group under the domain. We then installed the two cache devices into the group using their IP addresses. Once the cIQ Director communicated with the cache servers, summary status information flowed to the user interface. More detailed information is given when you view and edit the individual caches. But this information pulls the same Java applets that you would use when configuring individual devices. Those pages lacked the detailed information vCDN provided.
You create content-delivery jobs in the cIQ Director user interface by identifying the content via URLs, setting a schedule and initiating an action such as distribute, delete and revalidate--the same method vCDN uses. But the cIQ Director does not separate functions as vCDN does. Contents, schedules and actions are encapsulated in jobs. Although jobs can be replicated and the content applied to another schedule or delivered to other cache servers, the continuity of the content between jobs is lost. Editing the content of one job would not affect another job.
The cIQ Director contains a highly useful search tool. You can query individual objects in cache on one or multiple devices, then view, revalidate or delete them. We used this quick and dirty tool to remove or refresh Web objects from the cache on multiple servers. Neither Volera nor F5 supplies such a tool.
Although cIQ Director has fewer features than Volera's or F5's eCDNs, it does the basics quickly. You can enable and disable jobs, configure schedules and add and remove content from cache with little content creation and job handling overhead.
CacheFlow Security Gateway Appliance (CA-626), cIQ Director 2.0, (800) GO-CFLOW, (408) 220-2200; www.cacheflow.com or info@cacheflow.com
F5 Networks Edge-FX 540 2.2 and Global-Site 2.2
High price and quirky performance marred our experience with F5's eCDN solution. The Edge-FX 540 cache server provided minimal bandwidth savings on our simulated T1, though it fared better on the simulated T3 connection. In our network latency tests, it showed it has a long way to go before matching the performance of Volera's system, and, despite its $35,980 total price tag, it garnered the poorest P/E rating.
We tested two Edge-FX 540 cache devices and a Global-Site Controller. The Controller distributes content from origin servers to the cache devices. On each Edge-FX, approximately 114 MB of system RAM were devoted to RAM cache. All the appliances ran Linux Red Hat 7.0 (Kernel 2.2).
The Edge-FX uses Inktomi's Traffic Server caching system, which accepts connections, processes requests and serves objects from the cache. The server also features Traffic Manager, which commands and monitors Traffic Server's performance and configuration, and Traffic Cop, which monitors Traffic Server's and Traffic Manager's health. If the latter detects problems from "heartbeat" transaction requests, it restarts the server or manager process.
Like CacheFlow, the Edge-FXs were ready to cache as soon as we plugged them in, turned them on and set an IP schema. We attached a keyboard and monitor to the units, and a wizard stepped us through the configuration.
F5's Global-Site Controller moves content from origin servers to Edge-FXs like vCDN and cIQ Director. But Global-Site can obtain any file-based content and is not limited to URL gets, as vCDN and cIQ Director are. Therefore, it can obtain multiple files simultaneously. What's more, it can deliver to an Edge-FX cache server or another server.
Global-Site engages a number of steps to move content in the enterprise and uses a publishing paradigm. F5's "publications" are analogous to the Volera vCDN collections. These publications define the original content's source and transfer medium. Global-Site provides three options: FTP, FTP-Push and WebDAV (Web-based Distributed Authoring and Versioning) or WebDAV-SSL. With FTP and WebDAV, you can transfer multiple files in one request, though WebDAV requires a Global-Site agent on origin servers.
Global-Site's user interface could not manage multiple cache servers. We had to rely on the individual devices' Web-based administration tools. This solution, though adequate, lacked a single point of access to run content delivery end to end. The user interface could check for connectivity but couldn't view or manage cache server configurations. The interface did have the slick ability to map a URL to file-based information. After obtaining a file from disk, we input the URL that would identify the content to clients who requesting it through the proxy. In effect, this can turn the cache into a virtual HTTP server.
Global-Site Controller puts more control in content delivery than the cIQ Director does but less than vCDN does. But because F5 did not submit a utility to manage multiple cache servers (as the cIQ Director does), it trailed the pack in the management/configuration category.
F5 Networks Edge-FX 540 2.2, Global-Site 2.2, (888) 88 BIGIP, (206) 272-5555 www.f5.com or info@f5.com
Sean Doherty is a technology editor and lawyer based at our Syracuse University Real-World Labs®. A former project manager and IT engineer at Syracuse University, he helped develop centrally supported applications and storage systems. Send your comments on this article to him at sdoherty@nwc.com.
REPORTS
ANALYTICS
Follow 
