Electricity prices are rising, available supply is constrained in many regions. As rack density increases, power and cooling are critical concerns in data centers. Many data centers are simply out of power, to the point where organizations can only bring in new equipment by replacing old equipment. Devices with high power draw have direct and indirect costs that must be factored into data center design. Power-efficient products help minimize these issues. The power bill is not the only cost to consider in the data center — HVAC systems draw even more electricity as they work harder to remove more excess heat. If the current HVAC system is at capacity, non-trivial infrastructure investments may be necessary.
Power and Cooling Metrics of Fibre Channel Directors
|Ports, bandwidth |
|384 @ 8Gb (1.5:1)|
384 @ 4Gb (0.75:1)
|384 @ 4Gb (3:1)||128 @ 4Gb (1:1)|
256 @ 2Gb (2:1)
|140 @ 2Gb (1:1)|
70 @ 4Gb (1:1)
|132 @ 4Gb (1:1)|
264 @ 2Gb (2:1)
528 @ 1Gb (4:1)
|Watts / Port||3.5|
|Watts / Gbps||0.4|
|CO2 Emissions / yr|
1.6 kg of CO2 / Gb
2.5 kg of CO2 / Gb
8.3 kg of CO2 / Gb
12.1 kg of CO2 / Gb
|9.9, 10.7, 12.6 |
18.7 kg of CO2 / Gb
|@ 384p of 8Gb|
$4.58 / port
$0.57 / Gbit
|@ 384p of 4Gb |
$3.61 / port
$0.90 / Gbit
|@ 128p of 4Gb |
$10.98 / port
$2.75 / Gbit
|@ 70p of 4Gb |
$13.46 / port
$3.36 / Gbit
|@ 132p of 4Gb |
$26.73 / port
$6.68 / Gb
High power draw devices also limit rack density. Just because a rack full of devices can be powered on does not mean it can be properly cooled. The BTUs generated by inefficient equipment can overwhelm the ability of existing cooling mechanisms, forcing wide spacing or expensive layout redesigns. Both lead to inefficient use of valuable data center real estate.
Inefficient devices can cause data centers to exceed their existing "power budget" as well as strain the Uninterruptible Power Supplies (UPS) necessary for maintaining services during power outages and disruptions. High power draw directors can lead to infrastructure redesign. Adding additional power circuits, PDU, UPS and HVAC units is expensive as well as time-consuming as it often involves slow bureaucratic processes outside the control and budget of the storage group.
How does Brocade compare?
Brocade directors are the most power-efficient in the industry as demonstrated in the recent ESG Lab Validation paper. They have the lowest documented power draw at only 915 watts for 256 4 Gbit/sec ports and 1150 watts for 384 4 Gbit/sec ports. They require less power per port (under 4 watts per port) and less power per unit bandwidth than any other vendor. Brocade is the only vendor to require less than one watt per Gbit/sec of bandwidth. Even at 384 ports of full-speed 4 Gbit/sec, the SilkWorm 48000 only draws 1150 watts (or 750 milliwatts per Gbit/sec). In fact, ESG found that Brocade documentation was conservative, and measured power draw was even lower.
The Brocade DCX has even better power efficiency than the 48000, needing less than half a watt to deliver a gigabit of bandwidth. This is despite doubling the port speed and quadrupling the chassis bandwidth.
As a result, Brocade gets more done with less power as can be seen in the online port and power calculator. Compared to competitive directors, they generate much less heat, require less cooling and leave more power for other devices in a rack or a row. Competing directors only support a fraction of the bandwidth a Brocade DCX can deliver. Brocade allows for higher rack utilization and does not disrupt hot-aisle/cool-aisle airflow patterns.
Cisco directors are much less power-efficient than Brocade directors. According to Cisco's own documentation, the MDS 9513 draws more power per linecard* and two to three times as much power (over 3000 watts) than the Brocade 48000 or DCX. The MDS 9513 is much less efficient, drawing up to 16 watts per port, compared to 3.5 watts for the DCX. Since the DCX delivers much more bandwidth for much less power, at just 0.4 watts per Gbit/sec it is ten times as power efficient as the 9513 (over 5 watts per Gbit/sec). In fact, with the energy it takes to run just one MDS 9513, you can run a DCX and power a large American home.
The MDS 9513 draws so much power and generates so much heat that many OEMs will not allow more than one in a standard rack, or require they be installed in specialized racks that take up more than one floor tile.* While the side-to-side cooling is driven by fifteen fans, they are contained in a single field-replaceable unit (FRU) meaning all fans must be replaced when a single fan fails. Due to the heat generated by the high power draw, users have less than five minutes to replace the fan tray before the MDS shuts down.* Note that the Brocade DCX and 48000 have independent fan units -- if one fan unit is removed, the others provide adequate cooling indefinitely.
The extra space required by the MDS 9513's side-to-side and back-to-back airflow patterns sacrifices valuable rack space and floor tiles.* In comparison, three Brocade 48000s can be safely installed in a standard server rack with the side panels on. The high power draw of the MDS 9513 can be seen on the Cisco MDS 9513 Power Calculator, based on data from Cisco's own documentation.
The MDS 9513 has a much higher carbon footprint than the Brocade DCX, 48000 or Mi10000. Yearly CO2 emissions can be as over 12 metric tonnes per year,*, 8 metric tonnes higher than Brocade.
Cisco Director Power Claims - Fact or Fiction?
Brocade agrees users must consider their overall SAN architecture, and this means picking the most energy efficient building block. Whether a single unit or a fabric of a dozen, the Brocade DCX or 48000 are more power efficient than the Cisco MDS 9513. Unfortunately, Cisco also claims that a 120-port MDS 9513 draws "less than 930W". This claim is contradicted by Cisco's own documentation which estimates that a 120 port 9513 with 2 x 12 port linecards and 2 x 48 port linecards draws 1478 watts AC at 90% AC/DC conversion efficiency. (Remember that a fully configured 384-port Brocade 48000 director is documented at approximately 1127-1150 watts.) It is also contradicted by validated Brocade lab test data.
To ensure accuracy, Brocade hired an independent electrician to test both the Brocade 48000 and the Cisco MDS 9513 and found that the 120 port Cisco configuration actually draws 1347 watts, 45% higher than Cisco's claim of 931 watts. In fact, an empty 9513 draws more electrical current (5.6 amps) than a fully-populated 384 port Brocade 48000 (5.2 amps). Below is Brocade's test data. Where are Cisco's verified results?Lab Measurements of Fibre Channel Director Power Draw
|Energy / month||KWH||574||382||659||482||1730||734||574||734|
Cisco will claim VSANs help with power efficiency through consolidation. Like Cisco, Brocade can consolidate SANs using Virtual Fabrics.
Cisco's claim of efficiency in their December 2006 ESG paper is based on the assumption that Brocade would require 3 separate directors plus a router to do what Cisco can with three VSANs in a single MDS chassis. This is incorrect. Unlike Cisco and their Inter-VSAN Routing (IVR), Brocade does not need expensive licenses to share devices between software partitions. Device sharing between Brocade Virtual Fabrics comes built-in to Brocade FOS and is very easy to set up, as shown in the ESG Lab Validation Report.
Consider that the Brocade 12000 has 128 x 2 Gbit/sec ports and draws approximately 1800 watts, while the Brocade 48000 has up to 384 full-speed 4 Gbit/sec ports and draws approximately 1000 watts. If three administrators had three fully-populated Brocade 12000s as standalone directors, Virtual Fabrics would allow them to maintain their administrative privileges in a new 4 Gbit/sec fabric based on a single Brocade 48000. (This company would of course need a second parallel fabric for full redundancy as neither Virtual Fabrics nor VSANs provide protection against a chassis failure.) If a customer had a large core-edge fabric, the 1.5 Tb of switching capacity provided by the Brocade 48000 would allow substantial ISL reduction and profound power savings (up to 80% if an 8 x 12000 fabric were consolidated into a 2 x 48000 fabric).
Customers were able to see for themselves the power savings during the live demonstration of the Brocade 48000 versus the Cisco MDS 9513 at the Brocade booth at Storage Decisions Chicago in May. The power draw of the 9513 in these live tests matched Cisco documentation within +/- 5%. Cisco chose not to attend this event. Contact your local Brocade Sales Representative or Systems Engineer for more details on these power tests.
What About Advanced Functionality?
Cisco will claim that Brocade's testing was "simplistic" and that customers need to look at the SAN "holistically" and consider "advanced functionality" that is built into the MDS family. While Cisco directors can indeed enable SAN virtualization and distance extension, they need special linecards to do so. Not only do these linecards draw even more power than a standard MDS FC linecard, they also restrict the scalability of the 9513. If a Cisco MDS Storage Services Module (SSM) linecard or MPS 14/2 linecard are present to enable "advanced functionality" such as storage applications or distance extension, the MDS 9513 cannot have more than 252 ports active, less than half of the advertised maximum of 528.
Of course, Brocade also has special blades for the 48000 that enable virtualization, routing and distance extension. While they draw more power than a regular FC blade, these blades draw considerably less power than the equivalent Cisco linecards (as can be seen on the Brocade power calculator and Cisco's own documentation, and they do not sacrifice ports like the equivalent Cisco linecards. This port loss means that Cisco would actually need *more* directors than Brocade to scale out a fabric with advanced functionality for a given number of ports, drawing even more power.
Cisco will state that storage networking is a relatively small component of data center power draw. While the power draw of the SAN is less than storage and servers, data center and facilities managers are concerned over each and every watt and every BTU. As previously noted, higher power draw devices limit rack density (only so much power can be delivered to a rack) and force extra space to be used for cooling (only so many BTU can be extracted from a rack). With 33% more bandwidth per slot (64Gb vs 48Gb), three times as much overall bandwidth (1.5Tb vs 0.5 Tb) and a third the power draw, the Brocade 48000 is a more scalable building block, regardless of the scale, functionality or lifetime of the fabric. Holistically or not, Brocade can match the "advanced functionality" that Cisco claims, all while using far less power and for a much