Timothy
Parker Consulting Incorporated
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Questions and Answers Part 1 Welcome to the first in a series on technical Questions and Answers. The questions come from you, our loyal reader, and the answers will usually come from me, your humble (hah!) columnist. If you have any questions you would like answering in future columns, send them via e-mail to questions@tparker.com. (By the way, if you’re looking for the rest of the clustering series we started four issues ago, the entire series will be posted on my Web site www.tpci.com by the end of this month.) To lead off this series, I’ve chosen a number of short-answer questions to clear out my mailbox. We’ll lead off with a question that arose from my series on Gigabit Ethernet last year. Q: We want to upgrade to Gigabit Ethernet and have bought a bulk pack of compatible cards for new machines, but still have hundreds of older 10/100 Ethernet installe and working. Upgrading existing computers is out of the question. I need a switch that can handle 10/100 Ethernet and act as a bridge to Gigabit Ethernet at the same time. I really want to buy Canadian. Any advice? A: The switch that is top of my list for this use at the moment is from Plaintree Systems. They’re based on the Ottawa area and have been in the LAN business many years. I recently tested the Plaintree WaveSwitch 9224, which has 24 10/100 Ethernet slots on the front panel and up to two Gigabit Ethernet connectors on the back. The Gigabit Ethernet modules lip into the basic 10/100 switch and allow connecting between segments easily. Although not inexpensive, the WaveSwitch 9224 is a solid piece of equipment. Keep in mind the cable runs allowed by Gigabit Ethernet. The maximum distance allows with standard Multimode Fiber cable is dependent on the type of cable itself (not all fiber is the same!). The maximum length of Gigabit cables is 500 meters, but this is with the high-end cable. Most fiber cables are limited to about 220 meters. This can be an issue in most workplaces that have long runs between segment controller switches, so be careful which fiber cables you install. And remember to use crossover cables or switchable ports to join segments together! Q: Can I use one Linux-based server as my Web server, mail server, and Internet firewall? A: Yes, but you will want to be careful about the load you place on the machine. Acting as a firewall and connection to the Internet is itself a heavy task if there is a lot of traffic on the internal network. Add in the pressure of being a web server, and you may get an overloaded Linux machine. The best gauge of the Linux machine’s abilities comes from estimating the number of hits your Web site will receive and combine that with the traffic between the LAN and the Internet. If you expect only a few hundred hits a day, and your connection to the Internet will not be running at full capacity all the time, you’ll be safe with a low-power Pentium. For more traffic or more Web hits, bump the machine up to a faster Pentium. More important that the processor power is the amount of RAM in the server. It’s better to have a heavily-RAM equipped slower Pentium than a RAM-starved fast Pentium! Q: Which is the better base for a Linux machine? AMD Athlon or Intel Pentium? A: There are some versions of Linux that are optimized for the Athlon processor, but the performance difference between equivalent Athlons and Pentiums is small. What isn’t small is the price difference. Athlons are still cheaper than Pentiums. Both work well, and you will experience no compatibility problems with either CPU and readily available versions of Linux. Buy whatever is the best price. Better yet, spend the savings on RAM! Q: Are multiprocessor AMD Athlon systems available? I want to run some CPU intensive applications and need multiple CPUs for performance. What about multiprocessor Linux? A: There are some dual Athlon motherboards now appearing, and there are experimental versions of motherboard with up to eight Athlon CPUs on them, but none of these setups are readily available. Software to take advantage of the multiple Athlons is not available yet, although most multiprocessor code should work. At the moment, if you need horsepower, your best bet is the Intel line of chips, available in many configurations. Linux will support multiple processors, although the off-the-shelf Linux boxes are designed for single processors only. You have to pay a few more bucks for multiprocessing Linux, and my favorite vendor is TurboLinux (www.turbolinux.com). Q: I read your cluster series.
Can I mix different CPU speeds and vendors (Intel and AMD) in a cluster?
Is a dedicated subnet really necessary? A: Although the ideal Beowulf cluster has identical hardware with identical configurations. Still, for most purposes, mixes hardware and configurations is fine. Dedicated subnets will make machine-to-machine communications more efficient, especially with high-power workstations, but it is not a necessity. I run a cluster from a network 10/100 switch with no problems. |
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