Transcript Rackmount Basics

Rackmount Basics
By Gene Lee
July, 2002
Introduction
This presentation is designed to provide basic knowledge of
rackmount specifications, as well as demonstrations on the
installations of some of the commonly used accessories.
Although we try to cover all topics related to rackmount computer
chassis, please feel free to contact us should you come across
anything that you might need more assistance on.
The information given in the following sections is based on the EIARS-310 rackmount equipment specifications.
Types of Equipments
Cabinet
Cabinet is usually refer to a freestanding and self-supporting enclosure for
housing electrical and or electronic equipment. It is usually fitted with doors
and/or side panels, which may or may not be removable. A cabinet shall be
standard when it conforms to the dimensional requirements.
17.72” (450mm) min
Inside width
42U
U=1.75”
18.3” (465mm )min
Hole center to center
19” min
Ear to ear outside
dimension
An equipment or chassis in a typical cabinet can be mounted
fix by ways of using front mounting ears plus rear supporting
brackets. One can also place an equipment on angle supports
or cantilever shelves as well. However, the most common way
to mount rackmount computer or storage subsystems is by
sliding rails. Below photo shows 20” and 26” ball bearing rails
with quick-detach feature, AIC part number SR-20 (20”) and
SR-26 (26”).
The advantage of using slide rails is to allow
unit to be easily pulled out of cabinet for
maintenance. Also for heavier equipment
mounting is easier with sliding rails, without
having to hold on to the unit when mounting.
Photo to the right shows a 1U and a 2U
chassis with ball-bearing rails.
Rack
Rack is generally referred to the twopost style open-frame type as
opposed to the four-post enclosed
cabinet design. Rack could be with or
without casters. Since it has only two
mounting posts, equipments are
typically mounted by the front ears
along, or by the center-mount
brackets if the depth and weight of the
chassis requires a more balanced
mounting position. Cantilever shelves
are also widely used. It is also
referred to as Telco Rack, since it is
widely used in the telecommunication
industry to mount telephone relays.
To the right is a photo of a 35U open
frame rack with casters, AIC Part
Number: RACK-35U-OP
Cantilever Shelf
Center Mount
Rackmount Computer Chassis
People often have questions on what can be used in a rackmount
computer chassis. Years ago only single-board computer (SBC) along
with passive backplane were used in rackmount computer chassis. They
were mostly used to control machinery(automation), acquire data, or for
telecommunication applications (PBX). However, due to the coming of
the Internet era, requirements to house large numbers of co-location
servers drove the market to select something much more compact and
easier to manage. As a result many of the desktop servers got
transformed to the slim and rack mountable metal enclosures. The space
required for four desktop servers can easily house 40 rackmount chassis
in a cabinet.
The rackmount computer chassis we are seeing today is nothing more
than a desktop computer case with mounting ears and rails. Having said
that, it is definitely a much tougher task trying to pack same amount of
components into a slimmer environment.
We will try to cover the characteristics of each size of rackmount
computer chassis in the following few sections.
How to Select the Right Chassis
There are three important factors that determine which chassis to use:
1)Size of the motherboard
There are basically the following different standard sizes available today:
9” x 7.5” Flex ATX
12” x 9.6” ATX
9.6” 7.5”
•Mini Flex ATX
7” x 7” Mini Flex ATX
•Flex ATX
•Micro ATX
•ATX
13”
•Extended ATX
9.6” x 9.6” Micro ATX
12” x 13” Extended ATX or SSI EEB 3.0
9.6”
13”
9”
•SSI EEB V. 3.0
•SSI MEB – 16” x
13”
How to Select the Right Chassis – continued
In general anything that’s longer than the ATX size of 12” x 9.6” will need to
go into an extended chassis that’s at least 25” or more in depth. Some
motherboards that are slightly longer at 10.5” will mostly likely fit in a
shorter chassis at 21” of depth. As for SSI MEB standard of 16” x 13”,
AIC’s RMC4L-S4520 chassis is designed specially for Tyan’s S4520 quad
Xeon server board that comes in this form factor.
2) CPU Speed
It’s important to know whether a single or dual CPU based motherboard is
going to be used. Among the dual CPU’s, it’s also important to know
whether it’s for Intel Tualatin, Xeon Prestonia, or AMD Athlon MP. Different
chassis has different cooling design, especially in 1U where space is tight
and fans are limited in size. The following chart demonstrates a “Thermal
Scale” based on the available CPU’s on the market today.
More Fans Needed
Dual
Athlon
Dual
Xeon
Athlon
P4
Dual
Tualatin
Celeron
Tualatin
How to Select the Right Chassis – continued
When selecting the appropriate chassis for the processors, please also make sure to
select recommended CPU coolers. After all, cooling cannot be done on the chassis
along.
3) Capacity – expansion slots and drive bays
The last question you should ask yourself is: what about expansion slots and drive
bays?
Typically 1U can take one expansion slot and the most two, and 2U can most likely get
you two to three depending on the motherboards. When you need more than three
expansions, or when all expansion slots need to be at different bus clocks and voltages,
then 3U and higher where direct expansions are available will be your choice.
Drive bay arrangements vary from single HDD with slim CD-ROM to sixteen hotswappable drive bays with slim CD and FDD bays. Please make sure to always leave
yourselves room to grow when selecting drive bay configurations. When choosing
SCSI hot-swap option please make sure to use HDD with 80-pin SCA2 connector. For
IDE hot-swap option, AIC has a patent-pending adjustable backplane design that will
accommodate all brands of IDE HDD”s without using ribbon cable adapter.
How to Select the Right Chassis – Example
Here is typically how the chassis selection process begin:
Application Requirements - Please remember that a product always starts with
application, not from the chassis or motherboard :
Customer needs to build an email server for a small office of 10 people. He
is looking at a dual PIII/Tualatin board from Tyan – S2518UGN with SCSI
controller onboard along with two 1.13 GHz Intel Tualatin processors and
256MB memory. He will also need to run two 60GB Ultra-160 HDD’s in
mirroring, one CD-ROM and FDD, and one PCI Gbit Ethernet card for
bandwidth.
Step 1 – check motherboard size: This is a 12”(W) x 9.6” (D) standard ATX server
board. Therefore, we can use either long or short chassis.
Step 2 – check CPU type: Dual Tualatin configuration does not require a whole lot of
cooling efforts. Therefore, we do not need to choose chassis optimized for P4, Xeon,
or Athlon processors.
Step 3 – check expansions: Since customer only needs two SCSI HDD’s and one PCI
expansion, we can select one 1U chassis with at least two hot-swap SCSI HDD bays
and sufficient cooling for dual PIII.
Conclusion - RMC1M has dual SCSI hot-swap bays, slim CD and FDD bays, and has
six cooling fans, and since S2518 uses 25 degree slanted DIMM sockets cooling should
not be a challenge. If customer is not comfortable with 1U chassis, the closest 2U
chassis we can select is either RMC2M with 4 hot-swap bays, or RMC2N with 4 x 5.25”
bays and use BR-SCA23 for hot-swap bay conversions.
1U Chassis Basics
1U chassis is the toughest to build due to many size limitations. Although
1U is defined as 1.75”(44.45mm) high, the maximum height of the chassis
is actually at around 44mm which is approximately 1.732”, leaving just
about 0.45mm of clearance between every two 1U boxes. With the sheet
metal thickness at 1.2mm at top and bottom, we are left with only about
1.64” of net height for everything that needs to go into this box.
41.6mm = 1.64”
44mm
1.2mm
40mm Fan
As a result, the maximum height of any component that needs to fit in a
1U is at 1.6”. A full-size CD-ROM drive and a full-height HDD are all at
1.6” high. To allow better air flow, a slim CD-ROM drive and 1” HDD are
usually preferred.
1U Chassis Basics- continued
Also due to the height limitation, low-profile CPU coolers must be used in
1U. Preferably copper heat sink based CPU coolers are used for much
needed thermal characteristics. A right-angle riser card must be used to
provide expansion slot in 1U as well.
1U low-profile Copper heat sink CPU cooler
AIC Part # CPU-P4-FAN
1U Chassis - Expansions
1U chassis with it’s low-profile form factor provides space-saving
advantage over bigger chassis. In ISP’s co-location data center where
monthly charge is based on the amount of space occupied, 1U is often
the choice of many. Although cost of 1U chassis and associated
components typically are higher than that of 2U and above, the monthly
savings should pay for the higher initial costs in no time.
The disadvantages of 1U chassis are expandability and thermal. Majority
of 1U chassis can provide only one PCI expansion slot. However, AIC has
many 1U chassis that can provide two expansion slots. Here is a closer
look at RMC1N-XP chassis.
1
2
2
1
1U Chassis - Cooling
Thermal in 1U chassis has always been an issue for many people. The
newest technologies for cooling fans and blowers adopted by AIC along
with some proprietary innovative designs enabled us to conquered the
toughest cooling challenges to date. AIC’s patent-pending air-intake air
duct along with powerful exhaust fans provide the best cooling solution on
the market today.
2U Chassis Basics
.As you can see 2U chassis has much more room to work with, therefore,
it does not have as big of a challenge on cooling as 1U. 2U also has
more expansion capabilities.
1.2mm
Power
supply
8CM
Fan
Low-profile slots without
riser card
88mm
3 full-height expansions
via 3-slot PCI riser card
2U Chassis – Riser Cards
. any people have questions on how to use riser card. Riser card is
M
merely acting as an extension to the onboard PCI slots. There are
basically two types of riser cards available.
Active – uses PCI bridge on the riser card itself to provide IRQ signals
Passive – uses paddle boards to transfer IRQ signals from other slots off
the motherboard.
Due to the specifications of PCI slot, each slot only carries one IRQ
signal. Therefore, when putting three cards into one slot the additional
two IRQ signals must be routed from other onboard PCI slots.
AIC provides passive riser cards with paddle boards for costcompetitiveness reasons.
Photo to the right shows RC2017 riser card with 2 x 64-bit
PCI plus AGP Pro slots. This is
a “combo” card where two
distinct cards are combined into
one providing connections from
two different sources with
different bus clock and voltages.
2U Chassis – Riser Cards - continued
. etermining which motherboard is suitable to use which riser card is not
D
as difficult as many think. Below is a standard ATX motherboard from
Intel – SAI2. The circled mounting hole in the picture is on every
motherboard, and can be used to determine whether this board has the
right slot locations for riser cards or not.
1”
Onboard I/O ports
This mounting hole is the one
immediately following the onboard
I/O ports. Approximately 1” to the
left of this mount hole is typically
referred to as #6 or #2 slot,
depending whether #1 slot is
marked as the last one on the left
or the one right behind this
mounting hole. In either case, if
this is a PCI slot you will have no
problem using a standard riser
card. For the case where this slot
is either an AGP or missing
completely, you would need to
use an “offset” riser card for PCI
expansion, such as RC2-011 (32bit with ribbon bridge) or RC2-016
(64-bit with PCB bridge) riser
cards.
2U Riser Card Types
Below diagrams show the three major types of riser cards that AIC offers for 2U
chassis.
Riser Card Mounting Plane – Cannot Change
No Connection
IRQ Paddle
Boards
AGP Slot
AGP Slot
Extension
Ribbon Cable
Basic Type- directly connected
Offset type
Dual AGP+PCI type
Example:
Example:
Example:
RC2-007 : 32 bit x 3
RC2-011 : 32 bit x 3 with ribbon
RC2-013 : 32 bit x 2 + AGP
RC2-012 : 64 bit x 2
RC2-016 64 bit x 2 using PCB
instead of ribbon cable
RC2-017 : 64-bit x 2 + AGP Pro
3U Chassis Basics
.The significance of 3U chassis is that this form factor is the smallest one
can use without using riser cards for full size PCI expansions. However,
there is still a height limit of 3.9” on the expansion cards allowed due to
physical limitation of 3U form factor. Not needing riser card also has
another advantage, which is to allow expansions of PCI-X slots with
different speeds. Some high speed AGP PRO video cards also do not
work well with riser cards due to signal timing delays caused by riser
cards.
1.2mm
Power
supply
8CM
Fan
3.9” Max
132.5 mm
3U chassis also offers significantly more drive bays than 1U and 2U
chassis.
4U ~ 7U Chassis
4U chassis basically is the closest to desktop
computer chassis in dimensions. For that
reason AIC’s RMC4S can also be configured as
desktop or mid-tower computer chassis. 4U can
take pretty much any desktop components,
including PS/2 size power supplies and full-size
CD-ROM drives. Also, 4U can take 120mm fans
for high air-volume cooling.
5U is just a height-extension of 4U with one
extra “U” of space for additional drive bays. The
extended 5U chassis is often the popular choice
for telecommunication industry with 20 slot
expansions and large capacity redundant power
supply options.
7U chassis is designed to use height to
exchange for depth. For customer that needs
the capacity 5U extended chassis offers yet has
a 20” deep cabinet, 7U is the perfect choice with
double-deck design.
Hot-Swap Backplane
This section is designed to give some graphic illustrations on how to connect IDE
and SCSI backplane.
IDE – There is really no standard way to make an IDE HDD hot-swappable (or warmswap). Since data and power on the IDE HDD comes from two different connectors,
one needs to combine them to make one single hot-swappable connection. AIC
uses a 48-pin connector to combine the 4-pin power with the 40-pin data connectors.
Hard Disk Drive
Tray Mid-Plane
Since the data connector is fixed
and is located differently from brand
to brand, we use a patent-pending
design that allows up to 3mm of
adjustable lateral space to match
with any drive without using flexible
ribbon cable.
backplane
IDE HDD’s can be connected either with two devices per channel, I.e., Master +
Slave, or Master only with one HDD per cable. To do hot-swap it is recommended to
use only a single Master drive per cable.
IDE - continued
When using a typical two-channel IDE controller or RAID controller without hotswap, the cables are connected as follows:
ATA 100 HBA or
motherboard onboard
controller
Channel 2
Channel 1
Master 2
Master 1
Slave 2
Slave 1
This is the ideal setup for RMC1F chassis with four internal HDD bays.
IDE - continued
When using a typical four-channel IDE RAID controller with hot-swap support,
the cables are connected as follows:
ATA 100 IDE RAID
Controller
Master 1
Master 2
RMC1Q is ideal for this kind
of setup but with only three
hot-swap IDE HDD’s. For
RMC4D-IDE chassis user
can use two 8-channel IDE
RAID controllers to support
sixteen Master HDD’s.
Master 3
RAID 0 - striping
RAID 1 - Mirroring
RAID 5 – striping with parity
Master 4
It is recommended to use
round cables for easier
cable-routing and better air
flow.
SCSI Backplane
When choosing a chassis with SCSI hot-swap bays please use SCSI HDD’s with
SCA2 80-pin connector, which consists of 68-pin of data plus grounding and power.
The power pins are made slightly longer, so that when disengaging the HDD from
backplane, data pins would be disconnected first while power pins are still connected
for split of a second. This standard design enables a safe hot-swap interface for the
hard disk drives.
SCSI devices can be daisy-chained, and each channel can support up to 15 devices.
Therefore, when using a dual-channel controller one can select to run all the
attached devices all in one single channel, or split into dual channels for mirroring or
better performance.
Below shows how RMC1Q-SCSI chassis can be configured with a single cable.
HDD # 3
Female
Terminator
HDD # 2
HDD # 1
This configuration shows three single-bay SCSI
backplane daisy-chained with one single cable with
five connectors. Termination is done at the end of the
cable with a female terminator.
SCSI Backplane-continued
The following figures shows how RMC2D’s three backplanes can be connected as
single channel of 9 devices or dual channels of 3 + 6 devices.
HDD 7, 8, 9
HDD 4, 5, 6
OUT
OUT
HDD 1, 2, 3
OUT
male
Terminator
IN
IN
IN
Each backplane supports three HDD’s and only link cable is
needed to connect every two backplane.
HDD 1, 2, 3
HDD 4, 5, 6
OUT
OUT
male
Terminator
male
Terminator
IN
To HBA Channel 2
To HBA
HDD 1, 2, 3
OUT
IN
To HBA Channel 1
SATA
Serial ATA is a new serial I/O technology that utilizes point-to-point data
transmission method to get rid of the bus-arbitration and saturation bottlenecks
that typical parallel I/O devices face. Therefore each HDD must be connected
directly to a dedicated channel on a controller (HBA).
SATA RAID Controller
HDD 1
HDD 2
HDD 3
RAID 0 - striping
RAID 1 - Mirroring
RAID 5 – striping with parity
HDD 4
SATA also offers another
advantage over PATA or
SCSI as you can see from
the figure to the left, the
cable. Each SATA cable only
has 7 wires as opposed to
80 in the ATA100 cable. The
smaller cable makes cablerouting much easier, and
thus improve the air flow in
low-profile chassis such as
RMC1D and 2E where high
capacity drive bays are
designed