A $7,000 Server Comparison

After changing names several times in the past few years, IBM's Power-based servers are now known under the name IBM System p5. Because of the POWER5 processor's hypervisor, IBM was able to implement the 510Q's most distinguishing feature: LPARs. Short for Logical Partitions, LPARs allow up to 40 OS instances to share the same hardware without the need for any additional software. It even is possible to mix AIX, Red Hat Linux and SUSE Linux on the same server.

The 510Q is equipped with a POWER5+ Quad-Core Module. Due to cooling requirements, the processors in the 510Q are clocked at 1.65GHz—considerably lower than the dual-core model, which comes in 1.9 and 2.1GHz versions. Eight slots can house up to 32GB of DDR2 memory.

Disk storage is provided by up to four internal hot-swap Ultra-320 SCSI drives. Four PCI-X slots are available for expansion. The system also features two gigabit Ethernet controllers.

The back of the system also features two HMC ports. The HMC (short for Hardware Management Console) is a management system that can control up to 254 different LPARs running on up to 48 different servers. Unlike many other p5 models, the 510Q does not require an HMC to operate. Without HMC, the system partitioning capabilities are more limited, but basic features, such as remote console, work without issues.

The p5 510Q used in this review came with four 1.65GHz CPU cores, 6GB of RAM and two 73GB disks. The price was quoted at $6,971.

IBM currently supports AIX 5.2 and 5.3 as well as RHEL 4 and SLES 9 and 10. Gentoo, Fedora and Debian also offer PowerPC distributions. Again, this review is based on the RHEL 4 Update 4. The installation completed without issues and was the easiest installation in this review.

The Proliant DL140G3 is based on Intel's quad-core Xeon 5300 series. This chip essentially is two Core 2 Duo chips mounted on one carrier to fit into a single processor socket. HP has integrated two of these CPUs and up to 16GB of memory into a flat, 1U server. Two disks are available in hot-swap and non-hot-swap variants. The non-hot-swap configuration has space for two expansion PCI-Express slots. In the hot-swap version, one slot is used by an SAS controller. PCI-X variants also are available.

The DL140G3 used in this review was equipped with two Xeon 5345s, 12GB of memory and two hot-swap 36GB SAS disks. The quote came in at $6,531, making the DL140G3 the cheapest server in this comparison.

HP's Web site lists Red Hat Enterprise Linux 3 and 4 as well as SUSE Linux Enterprise Server 9 and 10, all in 32-bit and 64-bit variants. However, none of the 64-bit distributions will boot out of the box. Some searching on the HP Web site led to an advisory recommending disabling the BIOS setting for “8042 Emulation Support”. Once the option was turned off, the installation offered no additional surprises.

Reliability and manageability usually are considered the most important features for the proprietary systems. However, in recent years, management capabilities have increased on the x86-based servers. At the same time, the low-end systems in this comparison have lost many of these features their big brothers have. As an example, Sun's T1000 does not even provide hot-swappable disks.

For this reason, the tests in this article focus on performance, and the systems have to prove themselves in five different scenarios.

File compression is a CPU-intensive task with very low I/O requirements. The first test was run with a single bzip2 -1 (lowest compression) process compressing a 2GB file. This established the baseline performance for each system. Then the test is rerun with 2, 4, 8, 16 and 32 concurrent processes compressing the same 2GB file as before. These additional processes allow the systems to use more of the available processor resources. Because the processes are independent, scaling should be as close to linear as the hardware allows.

After the first run, all benchmarks were executed a second time at the highest compression level, -9. As the man page describes, the higher compression level significantly increases the memory usage of the process.

Figure 1. Comparison of bzip2 Low Compression Performance

Figure 2. Comparison of bzip2 High Compression Performance

The most interesting result in this test is the T1000. Just as Sun stated, the single-thread performance of the CPU is very weak. However, once 32 threads are being executed simultaneously, the system beats the rx2660.

The second interesting result is the DL140. As soon as eight bzip2 -9 threads are executed, the cache (4MB shared between each two cores) is no longer able to contain all data required. The performance hit is substantial. Although at low concurrency, the difference between low and high compression is below 10%, at 32 threads, the difference is 111%. The other systems show almost the same performance with both compression levels.