to Anonymous Coward - Memory & RAID Clarifications
Anonymous Coward asks, "The memory is DDR2, which I'm not familiar with, so would be interested to know if the individual banks (ie pairs of dimms) have separate channels, or whether the entire memory array has only 2 channels...?"
There appears to be 2 channels per socket.
http://www.sun.com/servers/x64/x4250/specs.xml
"Up to 64 GB (16 x 4 GB) of PC2-5300 667 MHz ECC fully buffered DDR2 memory"
http://www.sun.com/servers/x64/x4250/server_architecture.pdf
"Using a Sun StorageTek SAS RAID Host Bus Adapter (HBA), internal SAS disk drives can be configured for RAID 0, 1, 1E, 10, 5, 5EE, 50, 6, and 60 —when mirroring is implemented, drives are also hot-swappable."
Of course, some of the specs double with the X4450 (i.e. 4 quad core processors in 2U high, oodles of drives, 128 Gig RAM), as noted in the above white paper. Intel has not traditionally made 4 CPU sockets scale very well, unfortunately.
"Multiple, independent Front Side Buses (FSBs) that act as high-bandwidth system
interconnects. The Intel Xeon 5000 Sequence processors support both 1066 MT/sec and 1333 MT/sec Front Side Buses enabling theoretical data transfer rates of 8.66 GB/sec (at 1066 MT/sec) or 10.5 GB/sec (at 1333 MT/sec). The 7000 Sequence supports Front Side Bus interconnects at 1066 MT/sec."
The diagram for the 5000 sequence Intel processors (used in the servers reviewed by this article) implemented by SUN indicates that there are actually 4 memory channels, two for each front side bus, each memory channel operating at half the bandwidth of the front side bus. You can see this on pages 15 & 18.
If there will be an I/O bandwidth problem, it will be at the Intel Front Side Bus level... and this would only be accentuated in the quad-processor quad-core platform, which will be released soon, due to the decreased speed of the Intel Front Side Bus in the 7000 sequence processors. You can see this on page 21.