Datacenter-Link Blog

Server virtualization in Datacenters is one of the most implemented solution to make optimized utilization, improve efficiency and reduce consumption of the phisical infrastructure. While it is clear and well known to everybody what are the advantages of Virtualization from the IT point of view, the effects of virtualization on the physical layer of the datacenter are less popular. While having one single physical machine running one server means having one single point of failure (the machine) for each server, from an availability point of view, having multiple independent operative system (servers) running in one single physical machine, makes a larger number of servers dependend on one single point of failure (the machine). There are more Virtual servers than physical servers.
From this point of view it is more and more important to make the physical machine able to perform the necessary operations, for instance the shut down, while the multiple Virtual servers are running on it, and when critical power quality conditions exist.
UPS manufacturers for instance provide different client softwares which receive signals from their machines when the critical power event happens. Most of these Shut down clients are designed for traditional servers shut down. At this point we have to remember that between the phisical machine and the virtual servers there is an hosted or non Hosted application which needs to shut down after al the Virtual machines are turned off. It is more and more important to have clients able to shut down these applications which virtualize the hardware for each Virtual server, for example the VMware ESX or the Microsoft Virtual Server 2005 and perform a safe and complete software and hardware shut down.

Tags: availability, client, shut down, UPS, Virtual servers, VMware

Most technological environments use an under floor distribution technique to maintain the conditions within the built  environment.
The principle is simple and long established and uses the pressure underneath a raised access floor in order to ensure that cool air is available wherever an air outlet (usually a grill) is positioned. Maintaining good pressurisation is important in order for the air conditioning system to work efficiently. This aspect must be guaranteed for the entire life span of the room and be able to be modified over time.
The AFPS system (Automatic Floor Pressurization System) developed and tested by Uniflair ensures automatic adjustment to the air flow according to the servers installed enabling flexible installation regarding the infrastructure.
The AFPS ensures automatic adjustment of the air flow issued by the perimeter units with EC fans during ordinary andextra maintenance to maintain a constant under floor pressure by maintaining precise control of the air distribution / cooling in all of the room (eliminating Hot Spots). In fact, during ordinary maintenance, access raised floor panels are often replaced which therefore reduces the static pressure underneath the floor. As a consequence, the air flow issued by the grills is reduced and the risk of hot spots developing is increased. The control module, which can also be used with electronically commutated fans, allows a nominal pressure to be maintained underneath the access raised floor (from 20 to 80 Pa) and to manage the fan speed ensuring that the nominal pressure value (which can be set) is maintained during all of the operation phases of the unit during the life span of the room itself.
The system is composed of the following main elements:
1. Precision air conditioning units featuring modulating fan control (by means of electronically commutated fans);
2. Microprocessor regulation system with dedicated regulation software;
3. Pressure transducer which can be installed underneath the access raised floor and which is able to monitor the static pressure;
4. Pressure sensor with anti-fouling and “filtering” system of the moving components;
5. An assembly system for the pressure transducer ensuring reliable readings which are not influenced by dynamic effects;
6. A communication and management system of the LAN parameters integrated in the microprocessor control of the perimeter units.
The system manages the variations in pressure underneath the floor by means of an integrated system of automatic pressure regulation in order to deal with any eventual changes which are too rapid, therefore stabilizing the system. The system also manages the constant pressure underneath the floor during ordinary and extra-ordinary maintenance of the floor and also when new servers are installed, adapting the flow when:
• New equipment is added;
• The floor panels are opened during maintenance / installation of new equipment (without creating hot spots in another point of the same room);
• Partition walls underneath the floor break or are damaged.
The system can be integrated both with chilled water and direct expansion air conditioning units. In direct expansion units, the management software must allow for dedicated air flow regulation settings. The system is able to manage all of the information read by the different units and define combined regulation strategies by means of a LAN connection (Local Area Network); The system is able to manage the air flow of both a single unit as well as all of the connected units to ensure that the pressure underneath the floor remains constant; The system is able to define the nominal pressure value which is requested via the setting of the microprocessor control. The system is able to read the average pressure value of a specific area (one for each unit) with its management logic. The system may have a single point of reference in the room or may be managed according to various areas. In the second case, it is possible to control all of the units based on the average pressure read by all of the units with the exception of the areas in which the pressure “differs” too much from the average value. In this case, the units within this area manage the air flow independently in such a way that this specific single area also returns to a nominal value. The system manages the growth of the room over time: automatically changing the cooling capacity and the air flow depending on the number of units, grills and air distribution systems added.
The possibility of managing the air flow according to the growth of the room enables the absorption due to the fans to be reduced; in fact, when the room is not complete, the air flow needed is less than the nominal value, the AFPS system partializes the EC fans with significant benefits in terms of absorption. When there is a unit in stand by, it is recommended that it is kept switched on in order to optimise the energy efficiency , above all at partial loads.

In the electrical plants, where a high reliability is required from the power supply source because the operation cycle cannot be interrupted and the risk of a lack of power supply is unacceptable, an emergency line supply is indispensable to avoid the loss of large quantities of data, damages to working processes, plant stops etc. For these reasons, transfer switch devices are used mainly for:
• power supply of hotels and airports;
• surgical rooms and primary services in hospitals;
• power supply of UPS groups;
• databanks, telecommunication systems, PC rooms;
• power supply of industrial lines for continuous processes.
ATS010 is the solution offered by ABB: it is an automatic transfer switch system with micro-processor based technology which allows switching of the supply from the normal line (N-Line) to the emergency line (E-Line) in case any of the following anomalies occurs on the main network:
• overvoltages and voltage dips;
• lack of one of the phases;
• asymmetries in the phase cycle;
• frequency values out of the setting range.
Then, when the network standard parameters are recovered, the system switches again the power supply to the main network (N-Line).   ATS010 is used in systems with two distinct supply lines connected to the same busbar system and functioning independently (“island condition”): the first one is used as normal supply line, the second is used for emergency power supply from a generator system. It is also possible to provide the system with a device to disconnect the non-priority loads when the network is supplied from the E-Line. ATS010 device is interfaced by means of appropriate terminals:
- with the protection circuit-breakers of the N-Line and of the E-Line, motorized and mechanically interlocked, to detect their status and send opening and closing commands according to the set time delays;
- with the control card of the Gen set to control its status and send start and stop commands;
- with any further signals coming from the plant in order to block the switching logic;
- with the N-Line to detect any possible anomaly and with the E-Line to verifythe voltage presence;
- with an additional device to disconnect non-priority loads;
- with an auxiliary power supply at 24 Vdc ± 20% (or 48 Vdc ± 10%). This supply source shall be present also in case of lack of voltage on both lines (N-Line and E-Line).    

Tags: , Automatic transfer switches, electrical plants

One of the problems commonly faced during the design of a datacenter is the proper choice of the cabinet and before stepping into any decision it is necessary to consider all the different physical and environmental conditions that the new generation of active equipment requires.  Space optimization due to high costs of the infrastructure requires more concentration in the same cabinet therefore it is necessary to select cabinets with a minimum load bearing of 750 kls. Keeping unaltered the functionality of the cabinet itself: copper and fiber optics cable management, ant topple devices to prevent dangerous movement during maintenance operations. All the mobile components of the cabinets must be interconnected with the cabinet frame and this one put suitably to ground. This operation which is too often not properly carried out avoids electrostatic discharges when the percentage of relevant humidity falls between 45% and 50%. Today all server manufacturers recommend the maximum airflow to reach the electronics inside the cabinet.High rate perforated doors with a minimum empty surface of 80% installed on the front side of the rack fully comply with this recommendation and give the considerable advantage to check all the equipment “at a glance”. The same criteria is to be adopted on the rear part of the cabinet keeping carefully power and network cables out of the hot airflow and suitably cabled into proper management trays. It is clear how the new parameters change the previous layout based on the “chimney” effect using front glass and rear blank doors.The chimney effect shows us all the limits of this application even if still used in small installations: the performances of the  cold airflow coming from raised floor  directly inside the cabinet  it is easily compromised by heavy equipment that for obvious reasons is positioned at low level in the rack.Besides the reduced space between the door and the front side of the servers is not enough to guarantee the necessary airflow. Closing spaces on the 19”  can furthermore   prevent hot air coming from servers to go back on the front part of the cabinet causing “short circuits”.

Tags: , 19", air flow, cabinet, frame, perforated doors, rack