Issue 11, June 14, 1988 FRANK J. DERFLER, JR. CONNECTIVITY CLINIC High-performance networks tend to have dedicated file servers, but it is possible to increase throughput on your peer-to-peer network while keeping it cost-effective and flexible. CONNECTIVITY CLINIC NETWORK SPEED Our firm has six IBM PC ATs and a Compaq Deskpro 386/20 on an IBM PC Network using Version 1.10 of IBM's PC Local Area Network Program. I am beginning to realize how painfully slow this system is, especially when using shared databases. We want to add another computer to the network, but we've learned that IBM no longer manufactures the network adapter card we need. We have our software set up so that each PC can access information from portions of every other PC's hard disk, so software that requires a large centralized file server, such as NetWare, is something we would rather not invest in. We have a network capacity of 320MB spread throughout the system and don't want to invest in a file server with one large disk. Ideally, we would like a system that doesn't involve a tremendous hardware investment in boards for the individual PCs and allows us to use the PC Network coaxial cable we have already run to our 22 offices. Some of our attorneys have Macs at home, so we are also interested in network compatibility for Apple products. And we would like to see a substantial increase in file transfer speed with the new network. The research I've done so far seems to point me toward the IBM Token-Ring Network, but I'm afraid of being (expletive deleted) by IBM again. I understand IBM's PC LAN is now on Version 1.2, but I can't seem to find anyone who can tell me if it is any better than the older version. When I call IBM, they tell me to call a local dealer who can't seem to get any information out of IBM. --Rick Leeper Austin, Texas What a perfect letter for this connectivity blockbuster issue! Mr. Leeper, your letter gives me an excuse for taking the space to lay out some facts, and my opinions, about networking software and performance. I have some good news and some suggestions for improvement. First, IBM never made its now-defunct PC Network cards. They were, and are, made by Sytek Corp. Sytek will provide you with more cards and anything else you need to keep the network operational. The Sytek 6120 card is an improved version of the IBM network adapter card that you're currently using in your machines. Accommodating the Macs calling from home is easy, too. At night, set up a PC workstation running Remote or Carbon Copy. Both these programs can communicate with any kind of computer dialing into them, so the Macs will be able to use the network resources. It is much better to send keystrokes and screens through the phone lines than trying to exchange data packets. That is the end of the good news. The bad news is that after testing every network operating system we could lay our hands on, we found that LAN operating system software falls into two distinct categories: high performance with a dedicated server and mediocre performance on a peer-to-peer, or nondedicated, system. As your letter points out, peer-to-peer systems are flexible and economical. They work beautifully in office workgroup situations like yours. But the high-performance peer-to-peer resource-sharing LAN operating system you ask for is a contradiction in terms--high- performance operating systems rely on a dedicated server. It is very clear that the rated transmission speed of network interface cards is much less important in determining network throughput than the speed of the network operating system software and the disk drives. Using the same 8-MHz IBM PC AT as a server, software allowing nondedicated operation averages throughput in read/write activities that ranges (within about two standard deviations of the mean) from 90 to 170 kilobits per second. Software requiring dedicated operation (NetWare, VINES, 3+Share) averages a throughput of between 260 and 450 kbps. The type of interface card used causes the throughput to vary within a certain range, but the network operating system and the disk drive on the server set the range. Since you want to keep the flexibility of peer-to-peer networking, there are several things you can do to improve performance. (The results of our lab testing, using the 10-NET peer- to-peer operating system in various configurations, are summarized in the table ``Network Throughput,'' which lists the items in ascending order of cost and practicality.) First, install a RAMdisk on the servers and put the heavily used data files in the RAMdisk. This means you must install lots of extended memory in every server and follow strict administrative practices to copy data from the RAMdisk before shutting down. You can expect improved throughput of about 50 percent by operating from a RAMdisk. Second, when files are too big for a RAMdisk, install a disk cache program. Of many disk-caching programs on the market, 10-NET has the best we have seen. Using 10-NET's disk-caching program resulted in an average 10 percent improvement in random read/write tasks (more on sequential reads). Of course, you lose RAM to the disk cache, but you can put the cache in extended or expanded memory. Third, if a 10 percent increase in network throughput isn't enough, try the Awesome I/O. This product from CSSL Inc. (tel.: (213) 493-4818) is a soft˙00ware/hard˙00ware combination that reformats your disk and manages the BIOS for optimum efficiency. We found that the improvement in throughput ranged from 15 to 22 percent with this product. The Awesome I/O isn't compatible with every network, but it does work with well-behaved operating systems like IBM's PC LAN and 10-NET. Fourth, we tried using BatRAM from Santa Clara Systems (tel.: (408) 729-6700) as a server drive. BatRAM is a solid-state disk drive (up to 20 megs) that is battery backed and portable. Using BatRAM as a drive (it could also be a very big cache) gave us about the same improvement in throughput as using a RAMdisk: about 50 percent. BatRAM works with any well-behaved DOS-based network operating system. Expect about a 10 to 15 percent improvement in network throughput under NetWare, Version 2.1. You cannot add several of these options to accumulate the gains of each option. For example, using both the Awesome I/O and a cache on the network is likely to trash the system. Finally, some advice about tuning the network. The most primitive but effective method of ``tuning'' a peer-to-peer network is to arrange the files so that as little data as possible is pulled through the network. Keep as many application programs and private data files on local disks as is practical and use the servers only for data you must share. NETWORK YOUR QUESTIONS Connectivity Clinic gives you practical solutions to networking problems of all types. We'll pay $50 or more for any tips we print, plus an extra $25 if you submit your letter on a disk, and we'll gladly answer any questions you have, at no charge. We're sorry, but we're unable to answer letters personally. Mail your contributions to Connectivity Clinic, PC Magazine, One Park Avenue, New York, NY 10016, or you may contact Frank J. Derfler, Jr., via MCI Mail (be sure to use Derfler's box, named CONNECTIVITY CLINIC).