Dell PowerEdge M1000e Quick start guide

PowerEdge M1000e
Technical Guide
The M1000e
chassis provides
flexibility, power
and thermal
efficiency with
scalability for
future needs.

Dell
PowerEdge M1000e Technical Guide 1
This document is for informational purposes only. Dell reserves the right to make changes without
further notice to any products herein. The content provided is as is and without express or implied
warranties of any kind.
Dell, PowerEdge, PowerConnect, RapidRails, VersaRails, FlexAddress, and OpenManage are
trademarks of Dell, Inc. Avocent is a registered trademark of Avocent Corporation or its subsidiaries.
Other trademarks and trade names may be used in this document to refer to either the entities
claiming the marks and names or their products. Brocade is a registered trademark of Brocade
Communications Systems, Inc., in the United States and/or in other countries. Cisco and Catalyst are
registered trademarks of Cisco and/or its affiliates in the U.S. and certain other countries. Citrix®
and XenServer™ are trademarks of Citrix Systems, Inc. and/or one or more of its subsidiaries, and
may be registered in the United States Patent and Trademark Office and in other countries. Egenera
registered trademarks of Egenera, Inc. in the United States and/or other countries. InfiniBand is a
registered trademark and service mark of the InfiniBand Trade Association. Intel and Xeon are
registered trademarks of Intel Corporation in the U.S. and other countries. Mellanox is a registered
trademark of Mellanox Technologies, Inc. Microsoft, Windows Server, Active Directory, and Hyper-V
are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or
other countries. Platespin and PowerConvert are registered trademarks of Novell, Inc., in the United
States and other countries. Velcro is a registered trademark of Velcro Industries B.V. VMware is a
registered trademark and vCenter is a trademark of VMware, Inc. in the United States and/or other
jurisdictions. Dell disclaims proprietary interest in the marks and names of others.
©Copyright 2010 Dell Inc. All rights reserved. Reproduction or translation of any part of this work
beyond that permitted by U.S. copyright laws without the written permission of Dell Inc. is unlawful
and strictly forbidden.
Initial Release June 2010

Dell
PowerEdge M1000e Technical Guide 2
Table of Contents
1 Product Comparison ...........................................................................................5
2 New Technologies..............................................................................................7
2.1 Overview ..................................................................................................7
2.2 Detailed Information ....................................................................................7
3 System Information ............................................................................................9
3.1 Overview ..................................................................................................9
3.2 Product Features Summary .............................................................................9
4 Mechanical .................................................................................................... 10
4.1 Chassis Description..................................................................................... 10
4.2 Dimensions and Weight................................................................................ 10
4.3 Front Panel View and Features ...................................................................... 10
4.4 Back Panel Features ................................................................................... 12
4.5 Power Supply Indicators............................................................................... 12
4.6 Rails and Cable Management ......................................................................... 13
4.7 Rack Support............................................................................................ 16
4.8 Rack View ............................................................................................... 16
4.9 Fans ...................................................................................................... 17
4.10 Cabling................................................................................................... 21
4.11 Control Panel/LCD ..................................................................................... 22
4.12 Security.................................................................................................. 24
5 Power, Thermal, Acoustic .................................................................................. 26
5.1 Power Supplies ......................................................................................... 26
5.1.1 Supported Voltages .............................................................................. 27
5.1.2 Redundancy ....................................................................................... 27
5.1.3 Power Management .............................................................................. 29
5.2 Power Supply Specifications.......................................................................... 30
5.3 Heat Dissipation ........................................................................................ 30
5.4 Environmental Specifications......................................................................... 33
5.5 Power Consumption.................................................................................... 33
5.6 Maximum Input Amps.................................................................................. 33
5.7 Power-Up Sequence ................................................................................... 33
5.8 Acoustics ................................................................................................ 33
6 Processors and Memory ..................................................................................... 35
7 Midplane....................................................................................................... 36
8 Embedded NICs/LAN on Motherboard (LOM) ............................................................. 39
9 I/O ............................................................................................................. 40
9.1 Overview ................................................................................................ 40
9.2 Quantities and Priorities .............................................................................. 41
9.3 Supported Mezzanine Cards and Switches .......................................................... 44
9.4 I/O Module Installation................................................................................ 45
9.5 FlexAddress ............................................................................................. 45
10 Storage ........................................................................................................ 51
11 Video........................................................................................................... 52
12 Rack Information............................................................................................. 53

Dell
PowerEdge M1000e Technical Guide 3
12.1 Overview ................................................................................................ 53
12.2 Rails ...................................................................................................... 53
12.3 Cable Management Arm (CMA) ....................................................................... 54
12.4 Rack View ............................................................................................... 55
13 Virtualization ................................................................................................. 57
14 Systems Management........................................................................................ 59
14.1 Overview ................................................................................................ 59
14.2 Server Management.................................................................................... 60
14.3 Enclosure Management................................................................................ 61
14.4 Integrated Keyboard and Mouse Controller (iKVM)................................................ 65
15 Peripherals.................................................................................................... 68
16 Packaging Options ........................................................................................... 69
Tables
Table 1. Comparison of PowerEdge 1855/1955 Chassis and M1000e Chassis ............................5
Table 2. Rack vs. Blade Server Rack-Level Specification Comparison ...................................6
Table 3. Feature Summary .....................................................................................9
Table 4. Dimensions ........................................................................................... 10
Table 5. Typical Modular Server System Rack Height and Cable Reduction........................... 13
Table 6. Fabric Specifications................................................................................ 43
Table 7. FlexAddress Features and Benefits ............................................................... 47
Figures
Figure 1. Server Density Comparison ..........................................................................5
Figure 2. M1000e Front View.................................................................................. 10
Figure 3. Possible Server Module Sizes, Front Panel View ................................................ 11
Figure 4. Example Server Module Configurations .......................................................... 11
Figure 5. Power Supply Indicators............................................................................ 12
Figure 6. Rack Cabling ......................................................................................... 14
Figure 7. RapidRails Rack Kit Contents ...................................................................... 15
Figure 8. VersaRails Rack Kit Contents ...................................................................... 15
Figure 9. M1000e in a Rack.................................................................................... 16
Figure 10. Rear View Showing Fans......................................................................... 17
Figure 11. Blades, Blanks, and 1 Open Slot Needing to be Filled ...................................... 18
Figure 12. Power Supply, Power Supply Blanks, and Open Slot Needing to be Filled ............... 18
Figure 13. I/O Module and Open Slot Needing to be Filled ............................................. 19
Figure 14. Installed CMC, I/O Module, and Power Supply Blanks ...................................... 20
Figure 15. Installed iKVM Blank ............................................................................. 20
Figure 16. Power Supply, CMC, and I/O Module Blanks.................................................. 21
Figure 17. Simplified Cabling................................................................................ 22
Figure 18. M1000e LCD Panel Recessed Position ......................................................... 23
Figure 19. M1000e LCD Panel During Usage ............................................................... 23
Figure 20. LCD Panel Capabilities........................................................................... 24
Figure 21. Power Supplies in M1000e....................................................................... 26
Figure 22. M1000e Power Supply Rear View............................................................... 27

Dell
PowerEdge M1000e Technical Guide 4
Figure 23. Power Architecture .............................................................................. 28
Figure 24. PMBus Communication Channels ............................................................... 30
Figure 25. Server Cooling Air Profile ....................................................................... 31
Figure 26. I/O Module Inlet and IOM Locations ........................................................... 31
Figure 27. I/O Cooling Air Profile ........................................................................... 32
Figure 28. Power Supply Inlet and Cooling Air Profile ................................................... 32
Figure 29. Midplane........................................................................................... 36
Figure 30. M1000e Midplane Front View ................................................................... 37
Figure 31. M1000e Midplane Rear View .................................................................... 38
Figure 32. M1000e I/O Modules ............................................................................. 40
Figure 33. High Speed I/O Architecture ................................................................... 42
Figure 34. Ethernet Growth Path ........................................................................... 43
Figure 35. Difference Between Passthroughs and Switch Modules..................................... 44
Figure 36. FlexAddress Addresses........................................................................... 46
Figure 37. FlexAddress Screen in the CMC................................................................. 47
Figure 38. FlexAddress SD Card ............................................................................. 48
Figure 39. SD Slot on bottom of CMC....................................................................... 48
Figure 40. CMC FlexAddress Summary Screen............................................................. 49
Figure 41. CMC FlexAddress Server Detail Screen ........................................................ 50
Figure 42. Examples of Major Storage Platforms Supported ............................................ 51
Figure 43. M1000e RapidRails Static Rails ................................................................. 53
Figure 44. M1000e VersaRails Static Rails ................................................................. 54
Figure 45. M1000e Strain Relief Bar and Cable Enumerator Clip (12 Per Kit) ........................ 55
Figure 46. M1000e Mounted in the Rack ................................................................... 55
Figure 47. M1000e Strain Relief Bar and Cable Enumerator Clips...................................... 56
Figure 48. Examples of Major Virtualization Platforms Supported..................................... 57
Figure 49. Examples of I/O modules Recommended for Use in Virtualized Environments ......... 58
Figure 50. System Management Architecture Simplified Block Diagram .............................. 60
Figure 51. Chassis Management Controller ................................................................ 63
Figure 52. CMC Module Features............................................................................ 64
Figure 53. M1000e iKVM ...................................................................................... 65
Figure 54. Rear iKVM interface Panel ...................................................................... 66
Figure 55. Front Keyboard/Video Ports .................................................................... 66
Figure 56. Enclosure After Unpacking...................................................................... 69

Dell
PowerEdge M1000e Technical Guide 5
1Product Comparison
The Dell™ PowerEdge™M1000e offers significant enhancements over its predecessor, the 1955, as
can be seen in the following table:
Table 1. Comparison of PowerEdge 1855/1955 Chassis and M1000e Chassis
Feature
1855/1955 Chassis
M1000e Chassis
Blade Compatibility
PowerEdge 1855/1955
PowerEdge M600/M605
11G and beyond
Form Factor
7U
10U
No. of Blades
10
16
I/O Module Bay
4
6
Fabric Types Supported
1 x Dual GbE
1 x Dual Xaui
1 Lane –GbE, FC2
4 Lane –4 x IB
2 x 2 Lane to support:
GbE2 x 4
2 X 4 Lane to support:
1 Lane –GbE, 10GbE serial/KR, FC8/4/2/1
4 Lane –IB, 10GbE (Xaui. KR), 40GbE
Power Supplies
2 x (non-redundant) or 4 x 2100W PSUs
3 x non-redundant) or 6 x 2360W PSUs
Management Modules
1 (std) 2nd(optional)
1 (std) 2nd(optional)
KVM options
1 x Avocent® Analog or Digital KVM
1 x Avocent® Analog KVM (optional)
Putting 16 half-height blades in the PowerEdge M1000e is 60% more dense than using 1U servers.
Figure 1. Server Density Comparison

Dell
PowerEdge M1000e Technical Guide 6
Greater density means:
•Smaller Footprint
•More Processing Performance
•More RAM capacity
•Lower Power Consumption per unit
•Easier Manageability
Dell’s blade server platform offers superior feature density over comparable rack servers, as can be
seen from 0. (Darker blue shading indicates increased memory density.)
Table 2. Rack vs. Blade Server Rack-Level Specification Comparison1
R410
R510
R610
R710
R810
R815
R905
R910
M605
M610
M710
M805
M905
M910
Form Factor
Rack2
Rack
Rack
Rack
Rack
Rack
Rack
Rack
1/2
Blade
1/2
Blade
Full
Blade
Full
Blade
Full
Blade
Full
Blade
Processors
Manufacturer
Intel
Intel
Intel
Intel
Intel
AMD
AMD
Intel
AMD
Intel
Intel
AMD
AMD
Intel
Sockets
2
2
2
2
4
4
4
4
2
2
2
2
4
4
Max Cores
per 42U Rack
504
252
504
252
672
1,008
240
320
768
768
384
384
768
1,024
Memory
Max RAM per
rack, in TB
5
3
8
4
11
5
3
10
4
12
6
4
6
16
I/O
Max 1GB
Ethernet
Ports per 42U
Rack
252
378
504
420
588
588
320
440
512
640
576
512
512
640
Max 10GbE,
DDR IB, or FC
network
ports per
rack
84
168
168
84
252
252
140
220
256
256
256
256
256
256
Internal Storage3
Drives per
42U rack
168
252
252
168
126
126
50
160
128
128
128
64
64
64
Max 7.2k or
10k rpm
internal
storage per
rack
336
504
151
252
76
76
50
96
77
77
77
38
38
38
Max 15k rpm
internal
storage per
42U rack
101
151
37
76
18
18
15
23
19
19
19
9
9
9
Max SSD
internal
storage per
42U rack
17
25
25
17
13
13
0
16
13
13
13
6
6
6
1This rack-level physical capacity specification summary does not factor in power and cooling.
242U is the most common rack size.
3Storage measurements provided in Terabytes.

Dell
PowerEdge M1000e Technical Guide 7
2New Technologies
2.1 Overview
The PowerEdge M1000e is designed to help customers be more efficient with time, power and
cooling, investment, and system performance. It is a breakthrough Dell engineered and patent-
pending design that maximizes flexibility, power and thermal efficiency, system-wide availability,
performance, and manageability. The chassis integrates the latest in management, I/O, power and
cooling technologies in a modular, easy-to-use package. Designed from the ground up to support
current and future generations of server, storage, networking, and management technologies, the
PowerEdge M1000e includes the headroom necessary to scale for the future.
Dell optimized the PowerEdge M1000e Modular Server Enclosure and Server Modules to:
•Maximize flexibility—modular I/O, power, cooling, and management architecture.
•Maximize longevity—optimized power and cooling design supports current and future
generations of server modules and I/O. I/O bandwidth to support not only today’s generation
of 10Gb Ethernet, 20Gbps InfiniBand and 4Gbps Fibre Channel, but up to 40Gbps QDR
InfiniBand, 10Gbps Serial Ethernet, and 8Gbps Fibre Channel.
•Lower total cost of ownership (TCO)—lower cost than rack-mount servers with equivalent
features. Best in class power and cooling efficiency.
The PowerEdge M1000e Modular Server Enclosure solution supports server modules, network,
storage, and cluster interconnect modules (switches and passthrough modules), a high-performance
and highly available passive midplane that connects server modules to the infrastructure
components, power supplies, fans, integrated KVM and Chassis Management Controllers (CMC). The
PowerEdge M1000e uses redundant and hot‐pluggable components throughout to provide maximum
uptime.
The M1000e provides identical and symmetric fabric options B and C for each modular server.
Ethernet I/O switches support I/O sub-modules that provide external I/O flexibility of stacking ports,
10GE copper ports, or 10GE optical ports. True modularity at the system and subsystem level
provides simplicity of extension and enhancement, now and in the future.
The main benefits to customers of these features include improved:
•Data center density
•Power & cooling efficiency
•Flexibility
•Scalability
•Virtualization capability
•Ease of deployment
•Manageability
Together, these factors enable customers to do more with their server investment.
2.2 Detailed Information
Virtually unlimited in scalability, the PowerEdge M1000e chassis provides ultimate flexibility in server
processor and chipset architectures. Both Intel and AMD server architectures can be supported
simultaneously by the M1000e infrastructure, while cutting-edge mechanical, electrical, and
software interface definitions enable multi‐generational server support and expansion.
The chassis features:

Dell
PowerEdge M1000e Technical Guide 8
•A high-speed passive midplane that connects the server modules in the front and power, I/O,
and management infrastructure in the rear of the enclosure.
•Comprehensive I/O options to support dual links of 40 Gigabits per second today (with 4x QDR
InfiniBand®) with future support of even higher bandwidth I/O devices when those
technologies become available. This provides high‐speed server module connectivity to the
network and storage now and well into the future.
•Thorough power-management capabilities including delivering shared power to ensure full
capacity of the power supplies available to all server modules.
•Broad management ability including private Ethernet, serial, USB, and low-level management
connectivity between the Chassis Management Controller (CMC), Keyboard/Video/Mouse
(KVM) switch, and server modules.
•Up to two Chassis Management Controllers (CMC‐1 is standard, CMC-2 provides optional
redundancy) and 1 optional integrated Keyboard/Video/Mouse (iKVM) switch.
•Up to 6 hot-pluggable, redundant Power Supplies and 9 hot-pluggable, N+1 redundant fan
modules.
•System Front Control panel w/ LCD panel and two USB Keyboard/Mouse and one Video ―crash
cart‖ connections.

Dell
PowerEdge M1000e Technical Guide 9
3System Information
3.1 Overview
The Dell PowerEdge M1000e Modular Server Enclosure is a breakthrough in enterprise server
architecture. The enclosure and its components spring from a revolutionary, ground-up design
incorporating the latest advances in power, cooling, I/O, and management technologies. These
technologies are packed into a highly available rack dense package that integrates into standard Dell
and third-party 2000mm depth racks.
3.2 Product Features Summary
Table 3. Feature Summary
Feature
Parameter
Chassis Size
10U high rack mount
Blades per Chassis
16 Half Height, 8 Full Height
Total Blades in a 42U Rack
64 Half Height, 32 Full Height
Total I/O Module Bays
6 (3 redundant or dual fabrics)
Total Power Supplies
6 (3+3 redundant)
Total Fan Modules
9 (8+1 redundant)
Management Modules and Interfaces
2 CMCs (1+1 redundant), 1 iKVM, Front
Control Panel, Graphical LCD Control
Panel
AC Redundancy
3+3
2+2
1+1
Each requires power supplies in slots
1, 2, and 3 to be connected to a
different grid as compared to those in
slots 4, 5, and 6.
DC Redundancy
1+1
2+1
3+1
4+1
5+1
Each with one extra power supply that
comes online if one of the existing
power supplies fails.

Dell
PowerEdge M1000e Technical Guide 10
4Mechanical
4.1 Chassis Description
The Dell M1000e supports up to sixteen half-height or 8 full-height server modules. The chassis guide
and retention features are designed such that alternative module form factors are possible. The
chassis architecture is flexible enough that server, storage, or other types of front-loading modules
are possible.
4.2 Dimensions and Weight
Table 4. Dimensions
Dimension
Measurement
Width, not including rack ears
447.5 mm
Height
440.5 mm
Depth, Rear of EIA Flange to Rear of Chassis
753.6 mm
Total System Depth (Front Bezel to PS Latch)
835.99 mm
4.3 Front Panel View and Features
Figure 2. M1000e Front View
The M1000e enclosure supports up to 16 half‐height or 8 full-height server modules, each occupying a
slot accessible in the front of the enclosure. The enclosure has also been designed to accommodate
other form factors, including dual-width modules.

Dell
PowerEdge M1000e Technical Guide 11
Figure 3. Possible Server Module Sizes, Front Panel View
Server Modules can be freely located within each 2 x 2 half-height quadrant. The mechanical design
of the M1000e has support structures for half-height server modules above or below double-width
server modules, and for half-height server modules side-by-side with full-height server modules.
Figure 4. Example Server Module Configurations
Server modules are accessible from the front of the M1000e enclosure. At the bottom of the
enclosure is a flip-out multiple angle LCD screen for local systems management configuration, system
information, and status. The front of the enclosure also contains two USB connections for USB
keyboard and mouse, a video connection and the system power button. The front control panel’s USB
and video ports work only when the iKVM module is installed, as the iKVM provides the capability to
switch the KVM between the blades. For more information, see System Control Panel Features in the
Hardware Owner’s Manual.

Dell
PowerEdge M1000e Technical Guide 12
Fresh air plenums are at both top and bottom of the chassis. The bottom fresh air plenum provides
non‐preheated air to the M1000e power supplies. The top fresh air plenum provides non‐preheated
air to the CMC, iKVM and I/O modules.
4.4 Back Panel Features
The rear of the M1000e Enclosure contains system management, cooling, power and I/O components.
At the top of the enclosure are slots for two Chassis Management Cards and one integrated KVM
switch. The enclosure ships by default with a single CMC, with the option of adding a second CMC to
provide a fully redundant, active‐standby fault-tolerant solution for management access and control.
Interleaved in the center of the chassis are fans and I/O modules. This arrangement optimizes the
balance of airflow through the system, allowing lower pressure build-up in the system and resulting
in lower airflow requirements for the fans. For more information, see Back-Panel Features in the
Hardware Owner’s Manual.
4.5 Power Supply Indicators
Figure 5 shows the power supply indicators. For more information, see Back-Panel Features in the
Hardware Owner’s Manual.
Figure 5. Power Supply Indicators

Dell
PowerEdge M1000e Technical Guide 13
4.6 Rails and Cable Management
RapidRailsTM Static Rails for Square Hole Racks:
Supports toolless installation in 19‖ EIA-310-E compliant square hole 4-post racks including all
generations of Dell racks except for the 4200 & 2400 series
Has a minimum rail depth of 703 mm
Provides a square-hole rack adjustment range of 712-755 mm
Includes strain relief bar and cable enumerators for managing and securing cables
VersaRailsTM Static Rails for Square or Round Hole Racks:
Supports tooled installation in 19‖ EIA-310-E compliant square or unthreaded round hole 4-
post racks
Has a minimum rail depth of 703 mm
Provides a square-hole rack adjustment range of 706-755 mm
Provides a round-hole rack adjustment range of 706-755 mm
Includes strain relief bar and cable enumerators for managing and securing cables
One of the advantages of a modular server system is the reduction in cable management needs
within a rack system. The inclusion of fabric switches, integrated KVM and system management
aggregation at the CMCs provides six‐fold or better cable reduction. The following table shows a
comparison of a typical reduction available when using the M1000e Modular system with integrated
switches, compared to traditional ―rack and stack‖ components. The configuration in the table
assumes a server with four Ethernet ports and two Fibre Channel ports. In support of the M1000e,
Dell offers a modular system cable management system to ease system installation in Dell or other
industry-standard racks.
Table 5. Typical Modular Server System Rack Height and Cable Reduction
Component
Rack
Height
AC power
cables
Ethernet Cables
FC Cables
KVM Cables
2 socket server
1Ux16
2x16
4x16
2x16
USBx16 + VGAx16
KVM
1U
1
‐
‐
USBx1 + VGAx1
Ethernet Switches
1Ux4
1x4
4x4
‐
‐
FC Switches
1Ux2
1x2
‐
2x2
‐
Total Rack
23U height
39 AC cables
72 Ethernet Cables
36 FC Cables
USBx17 + VGAx17
M1000e Equivalent
10U height
6 AC cables
16 Ethernet Cables
4 FC Cables
USBx1 + VGAx1

Dell
PowerEdge M1000e Technical Guide 14
Figure 6. Rack Cabling
RapidRailsTM Static Rails for Square Hole Racks supports toolless installation in 19‖ EIA-310-E
compliant square hole 4-post racks including all generations of Dell racks except for the 4200 &
2400 series. Minimum rail depth is 703 mm. Square-hole rack adjustment range is 712–755 mm.
The rail system includes a strain relief bar and cable enumerators for managing and securing
cables.

Dell
PowerEdge M1000e Technical Guide 15
Figure 7. RapidRails Rack Kit Contents
Figure 8. VersaRails Rack Kit Contents
See Section 12 for more details.

Dell
PowerEdge M1000e Technical Guide 16
4.7 Rack Support
The M1000e chassis offers the following options for rack support:
•RapidRails™ static rails for toolless mounting in 4-post racks with square holes
•VersaRails™ static rails for tooled mounting in 4-post racks with square or unthreaded round
holes
See Section 12 for more details.
4.8 Rack View
Figure 9. M1000e in a Rack

Dell
PowerEdge M1000e Technical Guide 17
4.9 Fans
`
Figure 10. Rear View Showing Fans
The PowerEdge M1000e chassis comes standard with 9 hot-swappable, redundant fan modules that
are distributed evenly across the enclosure. The speed of each fan is individually managed by the
CMC. Together, these design innovations can provide:
•Significant power savings as compared to older servers
•Less airflow required as compared to the same number of similarly configured 1U servers
•A similar acoustic profile as compared to previous servers
Fans are N+1 redundant, meaning that any single fan can fail without impacting system uptime or
reliability. In the event of a fan failure, system behavior is dependent on the resultant temperatures
of the system, as monitored by the Server Module iDRAC and I/O Modules. The CMC continues to
interpret the airflow needs of each server and I/O module to control the fan speeds appropriately.
The system will not ramp the fans to full speed in the event of a fan failure unless deemed necessary
by on‐board monitoring. Failure of more than one fan will not automatically result in shutting down
of blade servers. This is because the blade servers have their own self-protection mechanisms to
prevent them from running too hot. The result of a failure of multiple fans would depend on the
configuration, ambient temperature, and workload being run. For example, the processors within a
blade are automatically throttled back by that server if they reach a thermal threshold and then shut
down if a critical over-temperature threshold is met.

Dell
PowerEdge M1000e Technical Guide 18
Note:
The blank blade, hard drive, and server I/O fillers for every blank slot are required for
cooling/airflow reasons.
Figure 11. Blades, Blanks, and 1 Open Slot Needing to be Filled
Figure 12. Power Supply, Power Supply Blanks, and Open Slot Needing to be Filled

Dell
PowerEdge M1000e Technical Guide 19
Figure 13. I/O Module and Open Slot Needing to be Filled