Lucid Nonsense


New Xserves

Tuesday, 7 April 2009

Apple have released new Xserves today. The new models are based on the same Nehalem based Xeon processors used in the recently released Mac Pros and similarly come in single processor quad core versions, or eight core versions sporting two of the CPUs. One significant difference with the Xserve CPUs over the Mac Pros is that the Xserves are sporting Xeon 5500 chips in all variants, whereas the quad core Mac Pro uses a Xeon 3500 series processor. Apart from having two QuickPath Interconnects versus the one on the 3500, the 5500 series processors also have a significantly lower TDP (Thermal Design Power), in theory making them run significantly cooler than the 5300 series, while using less power. The quad core Xserve does run at a lower clock speed than the quad core Mac Pro, 2.26Ghz versus 2.66Ghz or 2.93Ghz, but the TDP is around 50W lower, a not insignificant amount. The more heat a server produces the more that the air conditioning in a server room has to move, so people are increasingly looking at more efficient servers in order to cut costs. In server rooms where many servers are being used these cost savings can add up pretty quickly.

When compared to the previous Xserves the specs are reasonably similar although there are some obvious differences. The Nehalem architecture does provide a significant speed boost over the previous models, triple interleaved memory will lower RAM latencies, as with the new Mac Pros, and there are reductions in power used and heat produced. Interestingly compared to the Mac Pros the Xserves have either six or twelve RAM slots, evidently to push users towards speccing the RAM for triple interleaving, avoiding the situation possible with the Mac Pros where users could add more RAM into the four or eight slots and increase memory latency in the process. The other changes are not too surprising, as with the rest of the line the monitor connection moves to Mini Display Port, although annoyingly no DVI or VGA adapters are included in the box. The Xserve has now moved to a NVIDIA GeForce GT 120 for it’s graphics support, which matches with the standard Mac Pros, although that is likely to be fairly underused in most deployments at the moment. I assume that the reason for going with a reasonably specced dedicated graphics card, is to benefit from the inclusion of OpenCL in Snow Leopard, which will undoubtedly be released before the Xserves are next updated.

Other features remain fairly static. There are still three drive bays, albeit with 1TB modules now available and the expansion options, such as Firewire, USB and PCI-E, remain largely unchanged. There are two areas that are a little more interesting however:

Firstly there is now the option of adding a 128GB SSD. While useful from the point of view of lower seek times, very low energy usage and no mechanical parts, what is really interesting is that the SSD is installed as a 1.8” unit internally so doesn’t take up one of the drive bays. It will be interesting to see how accessible this unit is and whether it requires a specific Apple supplied 1.8” SSD, or if standard units can be used. I expect the former, but even so this is a great option, as it frees the drive bays to be used for data storage rather than for the OS itself. Splitting data and the system is generally a good idea, primarily for system performance, but with the previous systems this meant only two physical drive bays for data storage once the system was installed on the first drive. For data protection the other two drives were then normally configured as a RAID1 (mirrored), meaning that internal data storage space was in reality limited to 750GB. This meant moving to an external drive array for greater storage, and RAID units can be pricey. The Promise Vtrack RAIDs that Apple now sell start at around the £5000 mark (ex VAT) for the smallest 4TB version. With the SSD being used for the server OS, this now lets the Xserve’s internal drives be specced with up to 3TB of storage. Coupled with the optional RAID card, the Xserve can be specced with 2TB of RAID5 storage. While not a huge amount of storage it is sufficient for many deployments and RAID5 is a good balance between cost, storage and data protection. It gives the option of nearly three times the RAID-protected storage as before without having to resort to an external unit. This is oddly the first “real-world” benefit I could think of with this option, the fact that the system should run very nicely from the SSD is just an added bonus. It actually highlights one of the big benefits the G4 Xserves had; running with the cooler PPC G4 chips and not requiring the large front vents introduced with the G5 Xserves, those early Xserves had four drive bays.

Secondly Apple no longer sell their own SAS drives for the the Xserve. What has happened is that Apple are now selling SAS drives for the new Xserves that are created by Promise. What is weird is that Apple do not list these on the configuration page for Xserves on the online Apple store. This is a pain because:

  • You have to search separately for them, and not just for “SAS drive”, they’re listed as “Promise 450GB SAS drive”. I can see a few people ordering the wrong units here as there are a fair few different SAS options that come back on a search.

  • As you can’t order the SAS drives with the Xserve, if you want to spec your Xserve with three SAS drives you will also have to buy at least one of the standard SATA drives with the Xserve. You can’t configure Bay 1 as “None”. It’s not a big cost, but it’s a bit irritating to be forced to pay for something you don’t intend to use.

Still, apart from that small issue, it looks like a pretty good upgrade and the SSD option is something that I can see being useful, although as I intimated above more due to the added flexibility that gives with regards to storage than the obvious SSD benefits!

We will just have to await the inevitable benchmarks next once these make it out into the wild.


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