On Fri, Apr 03, 2009 at 09:14:24AM -0700, David Mathog wrote: > In the picture on the OP's link the external PS does not look any bigger > than a standard unit, which leaves very little room in it for the UPS > battery.
The picture shows 2 things sticking out. One is the PS, the one on the other side is a battery. There are 2 long wires (red,black) that run from the battery to the PS. I can't guess how long a battery of that size would last, but probably more than a couple of minutes. I'd bet that the main motivation for separate batteries was not cost, but the 5-8% PUE gain. Separate batteries must cost a lot more in maintenance and are less reliable, although a small failure that knocks out 1 node is preferable to a 1/N chance of failure of N nodes, if N is large. I'd also comment that the airflow is not clean front-to-back. The fans sit on the CPUs and blow down. This inhibits the front-to-back flow a bit. If you look in modern servers most of them have a fan blow front-to-back air over a tall heatsink over the processor. This is smoother flow, plus it allows redundant cpu fans. And as someone else mentioned, the airflow over the disks looks to be minimal. Disks don't need that much air, but many modern designs have much better disk airflow than this. -- greg _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
