|Ken Novak's Weblog
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Thursday, January 06, 2005
VM-based gateway to Grid computing: "Grid middleware is enabling resource sharing between computing centres across the world and sites with existing clusters are eager to connect to the Grid. However, the hardware requirements for access to the Grid remain high: a standard Grid-Ireland gateway requires four separate servers. We propose the use of Virtual Machine (VM) technology to run multiple OS instances, allowing a full Grid gateway to be hosted on a single computer. ..
We evaluate implementations of this architecture on two popular open-source VM solutions: Xen and User-Mode Linux (UML). Our results show that Xen outperforms UML for installation tasks and standard gateway operations. Performance is close to that of standard Linux, and more than acceptable for everyday use.
The Grid gateways support remote installation and management to facilitate integration with a national Grid infrastructure. Configuration is similar to that of sites running multi-computer gateways, making it easy to keep site installation profiles synchronised. Our VM gateway architecture provides a low-cost entry path to the Grid and will be of interest to many institutions.. " 11:49:46 PM
Windows vs. Unix software costs: Interesting analysis of a change that I've noticed in the last few years: Commercial Unix software is now cheaper than Microsoft software. There has been "price change - in opposite directions for Microsoft and the rest of the world. When you bought those 20 NT boxes to run SQL-server 7.0, say in March of 1999, those SQL-server licenses were a lot cheaper in both absolute and relative terms. SQL-Server 7.0 started at $508 per machine. You didn't need an enterprise class CPU license because users were counted as concurrent users [while now it counted as identified users] .. On the Unix side both the hardware and the software are cheaper today, but on the Windows side only the hardware is. ..
Unix software is now a lot cheaper than Windows software for similar levels of power and support. It's often not true among PC companies - HP and Adobe generally still charge more for their Unix products than their Windows products- but it is consistently true when you compare open market prices to Microsoft prices.
If you ask business people which costs more, Unix or Windows software, you usually get the kind of look reserved for idiots. Everyone knows Windows software is cheaper - that's a big reason so many people agreed to put up with the poor quality to begin with. Even three years ago that was true if you set scale aside as a consideration. Sybase for Unix was more expensive than SQL-Server for Windows - and people ignored the fact that Sybase served hundreds of concurrent users on big HP and Sun gear while SQL-Server worked for tens of people on Wintel gear. Today it's not true at any scale - and that's a big win for Unix." Why is this? My guess is the competition Unix is taking from Linux, which is cheaper still. Windows hasn't yet felt as much competition from Linux. 11:41:03 PM
Fiddler HTTP Debugger
: "Fiddler is a HTTP Debugging Proxy which logs all HTTP traffic between your computer and the Internet. Fiddler allows you to inspect all HTTP Traffic, set breakpoints, and "fiddle" with incoming or outgoing data. Fiddler is designed to be much simpler than using NetMon or Achilles, and includes a simple but powerful JScript.NET event-based scripting subsystem." Another key tool: IE 5 Web Developer Accessories
, including View Partial Source: "highlight the area of the Web page for which you want to view the source, right-click on it, and select "View Partial Source." [via John Sequeira] 3:27:06 PM
Understanding Citrix's SpeedScreen Latency Reduction (SLR): Description of how Citrix improves upon terminal server on high-latency links. Reminds me of mainframe terminals and the "local echo" and "keyboard lock" buttons! "Citrix has long talked up as a benefit of MetaFrame Presentation Server.. imagine a situation without SLR where a user is typing a document via an ICA session with 400ms of latency. .. To the user, it would appear that there is a half-second “lag” when typing.
To address this, SLR’s Local Text Echo causes the ICA client to behave a bit differently. When enabled, a user pressing a key on their keyboard causes that key code to be sent to the server. However, at the same instant, the local ICA client software also draws the appropriate character on the user’s screen even though the actual screen drawing instructions from the server are bogged down in the 400ms latency between the client and server. Then, once the ICA client finally receives the actual updated screen from the server, it doesn’t have to update that character on the local screen .. [It] works really well. It works with all different fonts and font sizes. .. complex things such as highlighting and deleting large chunks of text exhibit the lag associated with the actual latency...
The other major SLR feature is something called “Mouse Click Feedback.” This addresses another common problem in Citrix environments with high latency, namely, the fact that users click on a button, become impatient, and click on a button again before the first click registered. Then, when the application’s response finally makes its way to the user, whatever the user clicked on comes up twice. Mouse Click Feedback works by adding the hourglass symbol to the arrow cursor the instant the user clicks the mouse anywhere within the boundaries of the remote ICA application. [The mouse isn't locked, but users generally respond to the hourglass by waiting] ..
SpeedScreen is automatically used on a MetaFrame server whenever a user connects to a session that has between 150 and 500ms of latency. As long as the client supports it, it's used." In another article, the author notes that SLR consumes more bandwidth, sometimes as much as 20% more; thus it's a tradeoff of more bandwidth for less latency. 12:21:22 AM