Home Network Throughput

In a previous article, I talked about creating an MP3 server out of a Quadra 630. At that time, I asserted that it could handle the job but hadn't really tested it out. Now I'd like to put a few numbers on my Quadra's performance and talk about optimizing it.

AppleTalk has been around on Macs for as long as I've used them. When I first starting working with the SE and SE/30 in 1990, I could connect over the network to the server or use a shared LaserWriter. The protocol was designed when network bandwidth was low. It does a good job in tight quarters (say 230 kbps), but it is considered "chatty" at higher speeds. It has a lot of error correction and small packets, which ultimately slows it down on bigger network pipes like ethernet. So using Apple's personal file sharing over AppleTalk represents the low end of my Quadra's performance.

I tried three ways of changing the server to see the effect on performance.

I thought that quitting all background programs might free up more of the processor's time and make the server faster. Taking this idea to it's logical extreme, I substituted a ResEdit modified File Sharing extension in place of the Finder. I essentially had a Mac that looks like it has crashed on startup because it never even loads the Finder.

I doubted that the server would even work. Surprisingly, file sharing could serve files over the network without a problem. It also remembered all the Users & Groups information on the Mac. But the Quadra could not receive files. I suspect that the Finder is used for creating the new files. I was also surprised that copying 80 MB of files took exactly the same amount of time whether it was file sharing only or a normal Mac with all its usual software.

I don't know the specifics of why this worked out this way. I think that AppleShare is privileged and works before other programs get a chance at the CPU. It may have something to do with "high memory" that Conflict Catcher says AppleShare uses. Or that could be a coincidence. If any reader can explain it to me, I'll follow up this article.

My second method of performance tuning was Speed Doubler. Speed Doubler was a program that came with SurfDoubler. It runs on a server and speeds up networking for Macs with SurfDoubler installed. SurfDoubler has a network copy feature that increases throughput by substituting TCP/IP (the protocol of the Internet) for AppleTalk. Standard Mac OS 8 file sharing would write about 130 KB/sec. SurfDoubler let the Quadra write 200 KB/sec.

My third optimization was an old shareware program called PowerShare. The concept behind PowerShare is that it allows you to control how much of the processor is used for file sharing. Personal file sharing defaults to 50%. When I set the PowerShare control panel to 90%, the Quadra could write 190 KB/sec. When I combined PowerShare and Copy Doubler the Quadra wrote 220 KB/sec.

I don't have benchmarks for reading from the Quadra, but it was faster than writing. I suspect that reading is faster because it doesn't use the Finder and the cooperative multitasking. I also don't have benchmarks for different disk cache sizes, but larger disk caches do speed up file sharing as well. Or perhaps it's the converse: A small disk cache hinders file sharing.

What sort of performance is the Quadra doing? Even at it's best, the Quadra is still not saturating ethernet and will never replace a Power Mac G4 with gigabit ethernet. But it has enough bandwidth to serve the highest quality MP3s. It can handle JPEG files (for a picture frame) without breaking a sweat. It is on the verge of being able to reliably play MPEG files, which are traditionally encoded at the speed of a 1x CD-ROM or 150 KB/sec.

An avid Mac Collector set up a Quadra from his collection of Macs as a home MP3 server to his Performa 6500 and his iMac. He verified the general speed of the Quadra and tested reading and writing to the Quadra. From his 6500, he could read and write to the server at around 220 KB/second. His 2001 iMac was faster writing (280 KB/sec) and slower reading (180 KB/sec). There are lots of variables between the two clients, so I'm not concerned about the iMac being slower for reading. In either case, the Quadra is doing it's job in the same range of performance.

The server is also a reasonable backup device - I can back up 6-10 GB overnight depending on how I do it. In 2001 it seems to be all about G4s and Mac OS X, but a 68K Mac with Mac OS 8.1 can easily be useful, too.