Airsoft’s Powerburst

Revving Up RAS

Powerburst by Airsoft is a unique product.It's a remote-access accelerator. You can use it in both the Windows NT Serverand Novell NetWare environments to speed interactions between a remote clientand a file server. Powerburst improves performance by caching file accesses forthe remote server. This approach means the client cache can handle subsequentaccesses to a cached file so the server doesn't have to repeatedly retrieve thesame file remotely.

Conceptually, this approach is similar to how the Netscape Navigator cachesWeb pages as you cruise the Internet. However, the big difference--and the bigdeal--is that Powerburst ensures the accuracy of the data in the cache beforepassing it to the requesting application.

In the Powerburst architecture, remote access breaks down into threelogical functions, the file server, the client, and the agent. The file servercan be a NetWare server or an NT Server. To access the file server, clients usea dial-in link such as NT Remote Access Service (RAS) or a router or similarremote connection. In the version of Powerburst we tested (1.20), no specialsoftware is required on the server.

The client is the user system that initiates the remote connection, or inthe NT world, the client side of a RAS connection. Powerburst does most of itswork on the client: After you establish your RAS link, you activate Powerburst,and it enables the client-based cache. In the NT Server environment, Powerburst1.20 currently supports Windows 3.X and Windows for Workgroups (WFW) clientsconfigured for RAS support. By the time you read this article, a version ofPowerburst that also supports Windows 95 clients will be available. A timelineon planned support for Windows NT Workstation clients was not available at presstime.

The agent is a special Airsoft-created function that validates data toensure that the information in each client's cache is accurate and reflects thecorresponding information on the file server. A single agent can concurrentlyhandle up to 64 clients. In Powerburst 1.20, the agent software must run on aDOS-based system locally attached to the same LAN as the file server. By thetime you read this, you can expect a new version of Powerburst that lets you runthe agent as a virtual loadable module (VLM) under NetWare or as a service underNT.

The interaction between the client and the agent is the key tounderstanding Powerburst. On the client system, when you first start Powerburst,it begins building its cache of data as the client interacts with the remotefile server. When an application requests data that exists in the cache, theclient sends a terse, coded message to the agent. This message identifies thefile in question and the data area in the file. The agent then uses a local,high-speed LAN connection to check the data on the file server and reports backto the client. If the data is unchanged, the request is satisfied from the localcache. Otherwise, Powerburst retrieves the data from the file server andrefreshes its cache.

The assumption is that the client-query/agent-response approach is fasterthan retrieving the entire file over the remote connection. To further enhanceperformance, the client does look-ahead caching to predict future requests. Inmany ways, Powerburst's caching technique is similar to that of disk-cachingprograms, such as the DOS SMARTDRV program. The difference is that Airsoft hasdeveloped proprietary caching algorithms to address the unique characteristicsof remote access.

The Test
We tested Powerburst 1.20 on a DOS-based 60-MHz Pentium system as the agent,a 60-MHz Pentium NT server as the file server, and a 50-MHz 486 laptop runningWFW as the client. Powerburst came on two high-density disks: one for the agentand one for the client. The package included a thin, but fairly complete,manual.

The first decision was which protocol to use between the DOS agent machineand the NT server. Powerburst supports NetBIOS/NetBEUI and NetBIOS over TCP/IPin the NT environment. The DOS machine we used was already configured to runNetBIOS/NetBEUI with WFW, so we decided to take the path of least resistance. IfWFW had not been on that machine, we could have installed DOS LAN Managersupport from the NT Server distribution CD.

Installing the Powerburst agent software was simple and straightforward.After we installed it, we had to run a configuration program to define a namefor the agent. The agent name is really the NetBIOS name that the clients use toestablish sessions with the agent. Then, we rebooted DOS and brought up theagent by issuing three commands: netstartfull, share/l:500/f:5100, and pwragent

The netstartfull command activates WFW network support for DOS. Theactivation sequence prompts you for a username and password for your workgroupor domain. A critical requirement is that the username you specify hasread access rights to all the files that the remote clients potentially willaccess.

The Powerburst agent software requires share /l:500 /f:5100. This is a DOSterminate-and-stay-resident (TSR) service.

The pwragent command invokes the agent, which runs as a foregroundapplication. The agent software displays a brief configuration summary and thenwaits for an incoming client connection. This command doesn't establish aconnection to the file server until a client connection is made.

With the agent up and running, our focus shifted to the client environmentwhere we used WFW. A Windows-based setup program handles the installation of thePowerburst client software. This program copies the files to either a hard diskor a network disk. Then the setup program installs a new program group thatcontains Activate, Deactivate, Powerburst Control Panel, and Powerburst Helperapplets. Finally, the program modifies the Windows system.ini file and the DOSconfig.sys file. (Powerburst wants files=100 and buffers=40.) You need to rebootwhen the installation process is complete.

Before you can use the Powerburst client software, you must configure theagent name you set up in the agent software. The client needs this name tocommunicate with the agent. The client-to-server RAS connection can useNetBIOS/NetBEUI or NetBIOS over TCP/IP. We used NetBIOS/NetBEUI.

Before you start the client software, you must use RAS to establish a linkto the NT server and connect to one or more directories. If you attempt to startPowerburst before making these connections, you get a warning message sayingthat you don't have any remote file connections. After you connect to adirectory, you activate Powerburst using the Activate icon or through theControl Panel. The Powerburst client then establishes a session with thePowerburst agent, displays confirmation of the end-to-end connection, and thecaching process begins. Screen 1 shows the confirmation display.

Quick Cache?
The first time you run the Powerburst client, performance will be slowerthan usual because the client must build its cache, so that Powerburst cansatisfy read requests from the cache--if the requested information is there.Information in the cache is delivered to the application about twice as fast asover the remote access link.

For a simple test, we loaded a 90KB Word for Windows document over a RASlink, with and without Powerburst enabled. First, we loaded the document withRAS to establish a baseline time. Then we enabled Powerburst with an empty cacheto see how long loading the document and establishing a cache took. We loadedthe same document again to see how the Powerburst cache affected the load time.Our tests took the following times (in seconds):

RAS only (Powerburst not enabled):40.86

Powerburst enabled, no cache in place:58.11

Powerburst enabled, accurate cache:19.47

Loading the file from the Powerburst cache was approximately twice as fastas the initial RAS load. However, this was a best-case scenario. When we randomly added and deleted throughout the document, the client load time shot upto 46.38 seconds because most of the file needed to be reloaded. When wesignificantly changed only the second half of the file and then only the lastfourth, the load time stayed in the same neighborhood--51.87 seconds and 46.93seconds. The extent of changes didn't make much difference in the reload time.

In all fairness to Powerburst, focusing a test on the loading of a single,stream-oriented file is not a reflection of real-life performance. In real life,you work with a variety of files with several application processes. However,this test clearly shows the best and worst that Powerburst offers. You won't getbest-case--or worst-case--performance from all your remote-access applications.Real-life experience will fall somewhere between these extremes.

In the Right Direction
Does the fact that you won't get 100% performance improvement 100% of thetime invalidate the usefulness of Powerburst? Not at all. With repetitive workusing file-based applications such as Word for Windows, Lotus 1-2-3, MicrosoftMail, and dBASE over a remote link, this product will improve performance.

Even if you average only a 50% improvement, that's still a 50% advantageover a regular RAS link. Clearly, that's a step in the right direction.