The release of Apple's latest hardware offerings this month has caused quite a stir among Apple loyalists. This is only Apple's second foray into creating a truly dedicated server machine, the first of which being the "Network Server 500/700", which Apple sold in 1995 running AIX. The question on everyone's mind now is going to be what this means for Apple's prospects as a server platform. Certainly everyone agrees that the new machine looks nice, but how will it on the duties it will be required to perform. Furthermore, what kind of price/performance ratio is Apple offering when compared to the current group of servers.Even Steve Jobs, the master of spin, states that the Xserve device is not meant to be a competition with high end servers. In fact no one PC manufacturer puts up hardware that competes directly in the world of big iron servers. Mr. Jobs also is making sure that this isn't perceived as direct competition with middle-tier server platforms. These would be the multi-processor, multi-unit machines offered by other PC manufacturers such as Dell or Compaq. Instead, Jobs made it clear that this was Apple's first, and humble, push into the entry level server market.
Neither Apple nor Apple's faithful are naive enough to think that this one device will be able to please everyone. Just as in the design of every computer, Apple took trade-offs of performance and cost. Furthermore, Apple always has the stigma of not being an x86 platform in the minds of some people. What I am going to try to investigate is how Apple's offerings stack up against similar competitors in both individual components, software and in price.
To create a fair sample, I went to other major manufacturer sites--IBM, Compaq/HP, Dell and Sun-- and looked at all of their 1U rack mounted server offerings. I then went to Apple's site and pulled down their three recommended server configurations. Next, I attempted to recreate the offerings to match Apple's for each of the three configurations. This was the basis of the price/performance chart at the end. Of course, in and of itself this chart is meaningless without first looking at each of the individual components.
Processor
Apple of course is using the venerable PowerPC G4 running at its top speed of 1 GHz as the basis of the server. Each configuration is capable of housing two of these processors, however the low end configuration has only one at purchase time. The PowerPC chip itself is surrounded by benchmark controversy. How much power is the user going to get out of the PowerPC G4 when compared to the same offerings on the other platforms? This question is going to depend on how memory starved the G4 was with the old style memory bus. If the bottleneck was in the processor, and not in the memory system, then we can reasonably expect these G4's to perform on par with a mid-1.5GHz Pentium chip on normal operations, and maybe up to a 2GHz Pentium on certain optimized floating point operations. If there truly was a memory bottleneck in the old memory system, then the performance will be even higher. How high will be a question for the end users and benchmarks to determine.
In the case of IBM, Compaq and Dell, the processor of choice is the Intel Pentium III. None of the machines use the Pentium 4 or the Xeon version of each of these chips. The Xeon version of Intel's Pentium line basically adds larger caches to the chips, which allow them to keep more data readily available, without having to go out to the main system memory for data. The choice of processors in this case probably has to do with the heat dissipation requirements of having one Xeon chip, much less two, in the confined space of a 1U rackmount. If historical benchmarks are still accurate, these chips should give about the same performance as the 1GHz G4, however in memory intensive operation the 2MB cache on the Xserve's G4 may give it an extra performance boost. Also, as stated previously, the new memory system may make the G4 more effective than in previous benchmarks.
Sun's offerings of course use the UltraSPARC processor as the basis for its system. The UltraSPARC IIe is the chip of choice for sun's low end systems. This SPARC processor is hardly the same chip as the UltraSPARC III, which Sun puts in their high end machines. On top of this it runs at a relatively slow 500MHz. This puts Sun near the bottom of the heap on the processor power front. Although the benchmarks aren't as well studied in the Macintosh and PC circles, it has been stated that the UltraSPARC line is not as powerful as the PowerPC or Pentium lines in most operations.
Since the G4 in the dual processor Apple workstations, was recently defeated in multimedia benchmarks by a dual 1.5GHz Athlon, it will be interesting to see how the Xserve will benchmark against the single and dual processor Pentiums with their new memory subsystem. This will be especially telling with the very generous L3 cache in these systems as well. In the end, the new memory system could put the PowerPC back on par with current generation Pentiums and Athlons. Once again, only time will tell how much benefit the new memory system will give the Xserve.
Memory
One of the bigger sources of controversy in the Xserve is the memory system being used. With only one exception, the low end IBM web appliance, every single 1U system uses PC133 ECC SDRAM. For the uninitiated, this is error correcting RAM running at half the bandwidth of the RAM in Apple's system. Apple's RAM is PC2100 DDR RAM. This actually has the same clock speed as the PC133 RAM, but data transactions can occur twice per cycle, not just once. This is where the name "dual data rate" comes from. What this translates to is much higher performance than the SDRAM. However, this is not error correcting memory. This could be a relatively sore point for Apple to some potential customers. In some usages, large scale databases for example, it is not acceptable that the memory isn't error correcting. Time will tell if this was a wise decision on the part of Apple.
In terms of raw performance there is a great deal of benefit to be gained from using the DDR RAM. In the article "Inside RAM" on ExtremeTech.com, Jimmy Rimmer points out that DDR RAM not only provides a good deal of improvement on latency compared to SDRAM, but it also provides nearly double the bandwidth. On top of this, in real world usage, the DDR RAM can be almost as fast, or faster than the Rambus RAM in high end Xeon workstations. Performance-wise, this could provide a significant performance advantage to the Xserve on CPU intensive tasks. This trade-off will be more than acceptable for render farms and other users, who don't truly require ECC RAM.
- "Intro, CPU, Memory"
- "Disk I/O, Network Bandwidth, Software"
- "Price"
- "Conclusion"
