Home > Storage > PowerScale (Isilon) > Product Documentation > Storage (general) > Dell PowerScale: Considerations and Best Practices for Large Clusters > Power and cooling
In addition to available rack space and physical proximity of nodes, provision needs to be made for adequate power and cooling as the cluster expands. New generations of nodes typically deliver and increased storage density, which often magnifies the power draw and cooling requirements per rack unit.
The larger the cluster, the more disruptive downtime and reboots can be. To this end, the recommendation is for a large cluster’s power supply to be fully redundant and backed up with a battery UPS and/or power generator. In the worst instance, if a cluster does lose power, the nodes are protected internally by file system journals which preserve any in-flight uncommitted writes. However, the time to restore power and reboot a large cluster can be considerable.
Like most data center equipment, the cooling fans in a cluster’s nodes and switches pull air from the front to back of the chassis. To complement this, most data centers use a hot aisle/cold aisle rack configuration, where cool, low humidity air is supplied in the aisle at the front of each rack or cabinet either at the floor or ceiling level, and warm exhaust air is returned at ceiling level in the aisle to the rear of each rack.
Given the high power-draw and heat density of cluster hardware, some data centers are limited in the number of nodes each rack can support. For partially filled racks, the use of blank panels to cover the front and rear of any unfilled rack units can help to efficiently direct airflow through the equipment.
The use of intelligent power distribution units (PDUs) within each rack can facilitate the remote power cycling of nodes, if desired.
For PowerScale chassis-based platforms, where chassis depth can be a limiting factor, 2RU horizontally mounted PDUs within the rack can be used in place of vertical PDUs. If front-mounted, partial depth Ethernet switches are deployed, horizontal PDUs can be installed in the rear of the rack directly behind the switches to maximize available rack capacity.