Who: Tony, Anne & Dave with Jean-Claude Brahier. Main contact there was Udo Witkowski.
The Credit Suisse site in Horgen Oberdorf was planned in 1988 and construction finished 1994. One unusual problem is that it is sited near the trainstation and the major transformer/substation nearby led to many problems with electric fields in the air. The “surface habitable” is 17,000m2 of which the raised floor area is 4,250m2 spread across 6 rooms, of which 2 are unused at present. There is some office space, but much of the rest of the space is for the ancillary services.
The electricity comes over twin 22kV lines. Various figures for power consumption were mentioned so I’m not sure this is entirely correct. Site consumption is apparently 10MW. Of this, 50% is for cooling and ventilation—but this seems a high percentage. There is a 2MW UPS for equipment which provides 15 minutes autonomy. Although power consumption has decreased in past years, I’m not sure these figures really add up. [On a technical level, equipment has a capacitative cosf of 0.92, but the UPS capacity is inductive and has a cosf of 0.8. Whatever this means in detail, the net effect is a 25% loss in UPS efficiency. Anne comments that this has some relevance to the way load compensation is done at CERN and Credit Suisse…]
The UPS is, effectively, four parallel systems that each cross feed distribution boards in the machine rooms. This allows for some redundancy if one UPS module fails. Great stress placed on the superiority of Nickel Cadmium batteries over standard Lead batteries.
§ Lead batteries have a sharp voltage drop under sudden load. This can even drop below a critical value thus preventing the UPS providing AC power.
§ NiCad batteries can be guaranteed for up to 12 years with 20 years reasonable for total lifetime. This compares to lifetimes of 4-8 years for Lead batteries.
§ NiCad batteries are 3 times more expensive initially, but this looks good on the per-year of life basis.
§ Also stated that NiCad batteries take more space, but the volume of batteries for 2MWx15minutes didn’t seem to bad when we looked round.
There is a manual switch between the UPS supply and the public supply. This is turned to the public supply only as necessary—e.g. when UPS needs extending or somesuch. UPS is tested annually by manufacturer. This is visual inspection only; UPS is kept running.
Diesels provide the real backup for the power. Gas turbines are used at the other CS site in Zurich, but these don’t seem to offer (m)any advantages. The two diesels at Horgen will start within 50s of a power failure. There were some synchronisation problems with the diesels (made by EBB) initially, but not any longer. Whole chain stressed twice per year by running whole centre on the diesels after cutting the main supply. Additional tests performed each month involve running the diesels for a working day with a partial load. Much emphasis placed on regular “real world” testing of backup supply chain as opposed to annual inspection.
They have Emergency power off system at many levels—from main supply, to UPS, for each UPS module and out of UPS to rack. There is no legal requirement in Switzerland to test the EPO system annually; the design of the EPO circuitry is verified and certified before installation. [Apparently Credit Suisse are developing some special system to deal with short circuits in the UPS batteries. (lwhich lead to 8000A currents at 30V)…]
The air conditioning blows cold air from under false floor at 16°C. There are filters in each room and a good level of cleanliness (apparently approaching manufacturing cleanroom standards). In normal circumstances, there is little need for people to enter the rooms (operations are all remote); these are at the level of around 5 people/day. The exceptions are generally for equipment instalation. Air flow is apparently 10017912000m3/year; by my calculations, this is around 320m3/second.
Credit Suisse see that enclosed racks are often opened to allow cooling and that the air circulation of and within the racks is often poorly designed. Apparently in some other places they have installed water cooling systems in racks.
A Cerberus system provides a first level alarm following which checking is required by one of the permanent on-site security staff (no automatic call to fire brigade allowed…). A standard detection system is wired to the fire brigade with coincidence of two detectors required to raise alarm. (The alarm is also raised at the other CS site in Zurich.)
There is no automatic cut ot the electrical supply in the event of a fire alarm. However, as soon as there is an alarm, the air conditioning system stops adding fresh air (oxygen…). If the temperature and/or pressure rises beyond a certain threshhold then a venting system comes into operation to evacuate the smoke. Each of the rooms is isolated so there is no circulation of smoke between rooms.
There is an inter-bank exchange of information on fire risks to data centres. Apparently, most incidents are at the beginning—either of building life or equipment installation. It was mentioned that there have been two major fires at a new building before the fire detection equipment had been fully commissioned. At Horgen, new equipment is monitored very carefully for the first few hours, then carefully for the next few weeks before being considered a normal risk..
As the most common incidents are localised equipment overheating, CS have many fire extinguishers (C02 and Halon) that can be used by local staff following an alarm raised by the Cerberus detectors. A sprinkler system is installed in rooms foreseen for paper stockage, but not elsewhere. No “Hi-Fog” system is installed.