Even bigger than the issue of RAM usage is Apple's decision to offer the system with only Ultra ATA disk interfaces. Almost all the other selected systems, and most certainly the high end systems, all used Ultra160 SCSI drives. It is without question that the ATA disk interface is slower than the SCSI disk interface. On top of this, the drives themselves are only 7200 RPM drives, not the 10,000 RPM drives used in the competitor's 1U servers. The question is how this will affect the Xserve's overall performance.
Apple has addressed this issue in a few different ways. The first thing to notice is that the SCSI systems themselves only have one SCSI bus that all their drives attach to. The Xserve on the other hand has each ATA drive attached to its own interface. According to simple arithmetic, the combination of four ATA interfaces should provide a theoretical maximum data throughput of 266MB/s, compared to the Ultra160 SCSI maximum bandwidth of 160MB/s. On paper that sounds nice, but how the actual maximum translates into actual performance remains to be seen. If it works, it could provide a truly impressive disk I/O performance advantage for the Xserve, especially since the four disks act as one large disk via software RAID software built into the OS.
The first possible problem will occurs with the raw disk access speed itself. After a request for data, the Ultra ATA drives take a performance penalty compared to SCSI drives in their data access. A brief look at the statistical data compiled for all the fastest hard disks at StorageReview.com, show that even the fastest ATA drives pull in dismal performance compared to the top end SCSI drives. This is also true for total disk bandwidth and other benchmarks. The data also shows one other interesting thing however, Ultra160 SCSI drives don't always beat ATA drives, which are almost always significantly less expensive per megabyte. It is therefore possible, that the Xserve will be able to reach the same transfer rates as its SCSI-based cousins. The determining factor in this case will be the drive manufacturer used for the servers. It is therefore theoretically possible that the SCSI-based servers could turn in lower disk I/O performances than Xserve's ATA drives. Again, only time and actual use will tell us the rest of that story.
Network Bandwidth
With only one exception, the second generation Compaq servers, are the gigabit ethernet options standard outside the Xserve. In every other case, the gigabit ethernet is installed on the standard PCI buses of the systems, or it is not an option at all. This puts the Xserve at the top of the list in terms of network bandwidth. The Xserve has two gigabit ethernet ports, standard. One is directly integrated into the motherboard. The other is installed via the high speed 4xAGP/PCI bus slot. This gives the Xserve more network bandwidth potential than any other machine being reviewed. In some cases, such as the IBM machines, the systems could not be configured with more than one gigabit ethernet ports, however these systems generally had two on-board 100 megabit ethernet ports. The Sun server has by far the worst network performance, with no option for gigabit ethernet, and only two 100 megabit ethernet ports.
Software
Apple is shipping the Xserve pre-configured with MacOS X Server and all the necessary software to begin file serving, web server et cetera. Later this year Oracle will be done porting their database software to OS X, which will add high quality industry standard database serving to the list of tasks the Xserve can perform. Because MacOS X is Unix based, the underlying system has all the networking and file system performance which goes along with a Unix operating system. Apple has also packaged a software RAID solution to allow the operating system to see all the disks stored in the Xserve as one large hard disk. This offers all the standard RAID options that is typical of the standard hardware RAID systems. From a server software and operating system standpoint, Xserve gives the user quite a bit of quality software to work with.
Along with the operating system, the Xserve will have remote server management software. This will allow the operator to determine the operational status of each of the nodes, and each of the drives in those nodes, for the entire cluster of Xserves on the same network. This remote monitoring system is assisted by built in hardware monitors, which can help predict future problems on each of the nodes. This makes managing the cluster easier, however it doesn't help with controlling the distribution of tasks on a cluster of Xserves. Nothing in the documentation says anything about automatic load balancing in the operating system, or in any of the built in standard software packages.
The software situation on each of the other machines is variable. By default, the Sun machines have Solaris 9 and services associated with Solaris. This includes standard Unix utilities, such as Apache or POP mail. However, this doesn't include different windows connectivity software, or media streaming software, as on the XServe. In the case of the Intel-based servers, the software is configurable. In many cases, even if an operating system is purchased with the server, it is not installed by the manufacturer. This heavily impacts the instant usability of the other servers in the list.
The choice of software also is a problem when it comes to pricing the systems. Because Apple ships OS X with unlimited simultaneous users, the cost is fixed at the price of the server. Since Apple makes both the operating system and the hardware, the cost is the same as Sun's price--zero. However, in the case of the Intel servers, the operating systems come with user constraints on them. This heavily impacts the system cost. Operating system costs, even for many non-Windows options, can be anywhere between $700 and several thousands of dollars. This can translate into heavy cost penalties later on.
- "Intro, CPU, Memory"
- "Disk I/O, Network Bandwidth, Software"
- "Price"
- "Conclusion"
