Hot plug fan: Fan population and hot-plug support

Hot-plug fans

CAUTION: To avoid damage to server components, fan blanks must be installed in fan bays 1 and 2 in a single-processor configuration.

The only two valid fan configurations are listed in the following table.


Fan bay 1

Fan bay 2

Fan bay 3

Fan bay 4

Fan bay 5

Fan bay 6

1 processor

Fan blank

Fan blank





2 processors







For a single-processor configuration, four fans and two blanks are required in specific fan bays for redundancy. A fan failure or missing fan causes a loss of redundancy. A second fan failure or missing fan causes an orderly shutdown of the server.

Installing more than the required number of fans in a single-processor configuration is not a supported configuration.

For a dual-processor configuration, six fans are required for redundancy. A fan failure or missing fan causes a loss of redundancy. A second fan failure or missing fan causes an orderly shutdown of the server.

The server supports variable fan speeds. The fans operate at minimum speed until a temperature change requires a fan speed increase to cool the server. The server shuts down during the following temperature-related scenarios:

Are Hot-Swap Fans in Servers Still Required

Dell PowerEdge T630 open fan

As part of our reviews, we always highlight one server attribute: hot-swap fans. Fans are a hot topic because of a few notable characteristics. Modern fans, along with heatsink and other design elements, dictate the cooling capacity and the ability of the server to handle hot components. They can also have a notable impact on environmental attributes such as power consumption, vibration, and acoustics. A common question we would receive years ago was whether fans are hot-swappable in a server. This became such a prevalent question that it is one we regularly address in our reviews.

Over the past few months, I have been casually asking representatives from every major server vendor about fans. I have asked major enterprise customers as well as a few folks that work on servers from the “Super 7” hyperscalers. Though these discussions, I think it is worth starting a conversation on fans, and whether we still need hot-swap fans.

Why Hot-Swap Fans Matter

Hot-swap fans are excellent insofar as they enable a few different scenarios. Primarily, if a fan fails, one can replace the fan easily. That statement is usually true, but there are more factors. Fans are usually found in the midplanes of servers, such as this Lenovo example from our Lenovo ThinkSystem SR650 2U Server Review:

Lenovo ThinkSystem SR650 Delta Fans

One of the key factors there is that one needs to pull the chassis out of the rack, then open a cover, then replace a fan. Meanwhile, well-designed servers should be able to continue operating, but that is not always a given.

Netgear ReadyNAS RR4312X0 Hot Swap Fan Chenbro PCB

Great care has gone into designing different handles and connectors to make hot-swap possible, but one still needs to physically move a server to access the fan partition. If you do not have proper cable lengths, and/ or cable arms, you may end up with a hot-swap fan in a chassis that cannot be practically serviced while fully operational.

Gigabyte R281 G30 Four Hot Swap Fans

Other examples of why one may want to swap a fan can be for cleaning or if a server is being upgraded, higher-performance fans can be installed easily. These are corner cases and if one is upgrading CPUs or PCIe cards, the server is powered off anyway, making hot-swap unnecessary.

Dell EMC PowerEdge R740xd Hot Swap Redundant Fans

One thing is for certain, hot-swap fans to make servicing easier. Especially in denser fan configurations, having the ability to quickly remove a fan, often in one hand and with little effort, can mean greatly decreased service times. When a fan does fail, a replacement fan can be swapped out in under a minute if the rack environment is designed for hot-swap servicing.

HPE ProLiant DL360 Gen10 1P High-Performance Standard Configuration

The question is: do we still need hot-swap fans?

A Case Against Hot-Swap Fans

Although nice carriers make one excited for the mechanical design aspects, things have changed. Fans are one of the few moving parts, if not the only moving parts in modern servers with all-flash storage. They are indeed the only parts where a motor can stop working in today’s $100,000+ servers.

HPE ProLiant DL20 Gen10 Storage To PCIe Expansion Fan

Historically, fans were one of the parts that failed frequently, but this has changed. Electric motors and fans built around them are now extremely reliable. Advancements in materials and manufacturing have led to excellent reliability, especially outside of external aggregators such as debris getting into the rotating portion.

Just because a fan is not hot-swappable does not make it necessarily difficult to service. The above HPE ProLiant DL20 Gen10 fan takes seconds to replace. Likewise, the Dell Networking X4012 fan below takes longer to get to via chassis screws than the minute or so it takes to swap.

Dell X4012 Switch Fan Internals

In my travels asking people who make servers and who operate large data centers, fans have become very reliable. For example, one hyperscale datacenter tech told me that they keep no more than a few fans onsite as spares because they rarely fail.

Supermicro BigTwin SYS 2029BZ HNR Node Fan And Connector

We are seeing server designs like the HPE ProLiant DL325 Gen10, and even the Supermicro BigTwin we reviewed (see picture above) forgo hot-swap fans. When I ask if this configuration has been a problem on the service side, the answer is “no, fans rarely fail.” Indeed, some customers prefer their 2U4N platforms, like the BigTwin nodes shown above, to have fans on the nodes. This is because it is easier to service an entire node, including fans than to move the chassis out of the rack far enough to reach midplane fans.

Normally if I ask a question like this to 20-30 people, I get at least one outlier. At a minimum, I get a great anecdotal story of one customer one time with a machine. As I asked around, I never got that anecdote. Instead, the consensus is that fans rarely fail in servers. What that says, by extension, is that fans over the past few generations have been very reliable since we have not heard stories even dating back to the Xeon E5 days.

Final Words

Adding carriers and special connectors to both the fans and the motherboards may not be the largest cost per node. Today, the engineering for hot-swap fans is excellent. Designs from major vendors are easy to operate and work smoothly. The cost of mechanical design has been borne by generations of servers.

Ten years ago, when we started STH, hot-swap fans were a big deal. Not every vendor had a great design. There was an imminent risk of fans failing to the point our readers wanted us to highlight fans failing in our reviews. Now the questions we get are the opposite, are hot-swap fans still needed?

Inspur Systems NF8260M5 Hot Swap Fan

Today, the purpose of this piece is to ask whether the world has changed. Do we still need to highlight hot-swap fans in reviews? Should we consider them in our Design rating category? The more I got into this in informal interviews, since nobody wanted to share hard data, the more I have become of the opinion that hot swap does not necessarily matter. Instead, fans need to be easy to service. The standard 4-pin PWM connector for fans works well, but one also needs a system to manage fan cables if going that route. Perhaps the answer is that we do need hot-swap fans to aid robots in server manufacturing instead of for field service.

Personally, I think we need a new standard for fan form factors so server manufacturers can easily automate their installation, and fan manufacturers can standardize production. Fans last a long time, and are one of the most reusable parts in servers, especially given their reliability. Moving to a standard across servers that is easy to install and service will help the industry become more sustainable in the longer term.

Of course, if you have thoughts, feel free to discuss below, or in our forums which are a better venue for this discussion. I am sure folks have anecdotes with fan failures in modern servers or opinions on how to evolve cooling technology.

HP ProLiant DL380p Gen8 Server Hot Swap Fans

Material Information
Parent category: Files
Category: Manuals

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Configuration Socket 1 Slot 2 Slot 3 Slot 4 Slot 5 Socket 6 With 1 processor Empty Empty Fan Fan Fan Fan With 2 processors Fan Fan Fan Fan Fan Fan

For a single processor configuration, four fans and two empty bays are required in specific fan trays for redundancy. A fan failure or absence of a fan results in a loss of redundancy. Failure of the second fan or its absence causes an orderly shutdown of the server. Installing more than the required number of fans in a single processor configuration is not supported. For a dual processor configuration, six fans are required for redundancy. The failure or absence of a fan results in a loss of redundancy. Failure of the second fan or its absence causes an orderly shutdown of the server. The server supports various fan speeds. The fans run at minimum speed until a change in temperature requires an increase in fan speed to cool the server. The server shuts down during the following temperature-related scenarios:

  • In POST and OS, HP iLO performs a shutdown procedure if an elevated temperature is detected. If the server hardware detects a critical temperature level before the shutdown occurs, the server performs an immediate shutdown.
  • When the Thermal Shutdown feature is disabled in RBSU, then HP iLO does not perform a sequential shutdown when an elevated temperature level is detected. Disabling this feature will prevent the server hardware from shutting down to perform an immediate shutdown when a critical temperature level is detected.

WARNING: A thermal event can damage server components when the Thermal Shutdown feature is disabled in RBSU .

Continuation here

Table of Tempic


Designation of components

Components of the front panel

Indicators on the front panel and buttons



Protective panel

Access to the rear panel

Removing the hot replacement fan

Removal of the fan for hot replacement

Removing the full -format expansion fee

Removing the PCI RISER

installation PCI RISER 9003 Full Frame Expansion Card

Removing the Air Baffle


Configuring the HP ProLiant DL380p Gen8 Server

Optimal environment

Requirements for temperatures

Requirements for nutrition

warnings on RACK

Supply set

installation of the server in the stance

Operating system installation


Hot Plug Disk Options

Controller Options

Cache-to-Flash Backup Writer Installation

Install flash-backed write cache capacitor pack

Optical drive option

Redundant hot-swap power option

48 volt DC power option

FlexibleLOM options

Expansion card options

PCI riser19

Secondary cage option

Secondary cage option

Hard drive cage options

2U rack bezel option

HP Trusted Platform Module options

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    NR-N4800 | NegoRack

    For storage and video surveillance servers

    Great solution for 4U platform. The design of the case allows you to install full-sized EATX motherboards up to 12″x13″ in size.

    A 12cm fan and two 8cm fans on the back provide excellent airflow inside the case. The airflow from the 12cm fan is directed specifically to cool additional expansion cards, such as a video capture card.

    Four 5.25″ bays provide ample storage space. The case comes with a removable basket for installing 5 3.5” drives, which is installed in 3 5.25” bays on the right side of the case.

    If required, the chassis can be supplemented with hot-swappable hard drive cages.

    Two front doors, each with an easy-to-change dust filter. The doors are locked with a key to avoid unauthorized access.

    Can be installed in server and telecommunications cabinets with a depth of 800 mm or more.

    Supports most modern motherboards.

    Supported form factors:
    EATX (12″ x 13″)
    microATX (9.6″ x 9.6″)
    SSI CEB (12″ x 10. 5″)
    ATX (12″ x 9.6″)

    Can accommodate additional 5.25″ devices such as «hard drive cages»

    High data density

    A maximum of 7 3.5″ drives can be installed. Two regular 3.5″ bays and a basket for five 3.5″ drives, which is mounted in three 5.25″ bays (supplied with the case)

    The use of standard power supplies allows you to reduce the cost, and also makes it possible to choose a replacement in the event of a power supply failure.
    PS/2 power supplies 140mm or 165mm deep; with fans 80mm, 120mm.

    A redundant power supply is available to provide maximum system resiliency.

    One 120mm fan on the front panel and two 80mm fans on the rear panel, in combination with the power supply fan, provide stable cooling and airflow for all system elements.

    Washable, quick release, in front doors

    The case is equipped with expansion card retainers at the top and front.