Application Notes -
Data Replication Manager Using Very Long Distance GBICs
Part Number: EK-DRMLD-AA. C01
Second Edition (September 2001)
Product Version: ACS Version 8.6P
This document summarizes the performance considerations, power budget, and fiber link budgets for the
Very Long Distance GBIC that is available for the Data Replication Manager.
For the latest version of these Application Notes and other Data Replication Manager documentation, visit
the Compaq storage website at:
http://www.compaq.com/storage/san-mgmt
b
2001 Compaq Computer Corporation.
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All other product names mentioned herein may be trademarks of their respective companies.
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12.211 and 12.212, Commercial Computer Software, Computer Software Documentation, and Technical Data for
Commercial Items are licensed to the U.S. Government under vendor's standard commercial license.
Com paq shall not be liable for technical or editorial errors or omissions contained herein. The information in this document is
provided "as is" without warranty of any kind and is subject to change without notice. The warranties for Compaq products
are set forth in the express limited warranty statements accompanying such products. Nothing herein should be construed as
constituting an additional warranty.
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Printed in the U.S.A.
Application Notes - Data Replication Manager Using Very Long Distance GBICs
Second Edition (September, 2001)
Part Number: EK-DRMLD-AA. C01
2 Application Notes - Data Replication Manager Using Very Long Distance GBICs
About This Document
About This Document
These application notes provide an overview of the Very Long Distance GBIC (Gigabit Interface
Converter) that is available for the Data Replication Manager (DRM). DRM is a storage-based data
replication and workload migration solution that copies data online and in real time to remote locations
through an extended Storage Area Network (SAN). The Compaq SANworks Very Long Distance
GBIC has not been qualified for configurations other than the Data Replication Manager.
For complete details on the DRM, refer to the Compaq SANworks Data Replication Manager HSG80
ACS Version 8.6-1P Configuration Guide and the Compaq SANworks Data Replication Manager
HSG80 ACS Version 8.6-1P Failover/Failback Procedures Guide. For a list of additional software
support required for each operating system in your DRM solution, go to the following website:
http://www.compaq.com/products/sanworks/drm/index.html
Follow the Software Support Matrices link, then choose your operating system under ACS 8.6-P.
This application note contains the following sections:
O v erv i ew
Data Replication Manager
Performance Considerations
Power Budget
Examples of Fiber Link Budgets
Ordering Compaq SANworks Very Long Distance GBICs
Laser Safety Compliance
Website
Overview
The Compaq SANworks Very Long Distance GBIC is a serial-electrical-to-serial-optical transceiver
module, which operates at 1062.5 megabits per second. It provides optical link lengths for ANSI
X3T11.2 Fibre Channel applications between 10 and 100 kilometers, depending on dB loss in the link.
Figure 1 shows a typical DRM configuration using the Compaq SANworks Very Long Distance GBIC
9-micron single-mode fiber with SC connectors.
Application Notes - Data Replication Manager Using Very Long Distance GBICs 3
Data Replication Manager
Network Interconnect
Host Host
Switch A Switch Y
~
~
Ver y Long
Up to 100 km 9 micron
Distance
single-mode fiber
GBIC
Controller A Controller Y
Normal
GBIC Switch B Switch Z
~
~
Up to 100 km 9 micron
single-mode fiber
CXO7162B
Figure 1: Data Replication Manager using Very Long Distance GBICs
Data Replication Manager
During normal data processing, data is simultaneously written to initiator (local) and target (remote)
sites. While copies of data reside at both sites, host data access occurs through the initiator site, unless
a failure or a catastrophic event disables processing at that site. In the event of an initiator failure, the
target site can continue processing data in the interim.
The DRM provides rapid data access recovery and continued data processing after the loss of one or
more components. The DRM uses the peer-to-peer remote copy function of the HSG80 controller to
achieve data replication. HSG80 controller pairs at the initiator site are connected to their partner
HSG80 controller pairs at the target site.
The DRM can replicate data at distances up to 100 kilometers (approximately 60 miles) through an
extended Storage Area Network over direct Fibre Channel links that operate at 10 to 100 megabytes
per second, depending on distance.
4 Application Notes - Data Replication Manager Using Very Long Distance GBICs
Performance Considerations
Very Long Distance GBIC Product Features
The following features are supported:
Fibre Channel at 1062.5 megabits per second
Distances of 10 to 100 kilometers over 9-micron, single-mode fiber-optic cable
1550-nm center optical wavelength
Integration of a distributed feedback (DFB) laser
Serial ID functionality
Low power consumption (800 mW typical)
Duplex SC optical port
Hot-pluggability
Performance Considerations
Fibre Channel has a credit-based flow control. The Compaq SANworks Very Long Distance GBIC
extends the distance between the Fibre Channel switch E_ports. The credit given on the E_port is eight
buffer-to-buffer (bb) credits. Currently, eight buffer-to-buffer credits are the maximum number
assigned. Efforts are underway to improve throughput at long distance.
Figure 2 shows that with eight buffer-to-buffer credits, the throughput diminishes with increased
distance.
PRELIM INARY FC THROUGHPUT M EASUREM ENTS
120
100
Throughput (MB/s)
80
8 bb credits
60 24 bb credits
50 bb credits
40
20
0
0 25 50 75 100
Di sta nce (km)
Figure 2: Credit-based flow control
Application Notes - Data Replication Manager Using Very Long Distance GBICs 5
Power Budget
Power Budget
The link power budget is the power available to transmit light over the link. The power budget of the
Compaq SANworks Very Long Distance GBIC is 24 dB, minimum.
The following should be considered when calculating link distances:
Power budget
Connections
Sp l i ces
Fiber attenuation
Figure 3 shows typical mean loss in dB for connectors, mechanical splices, and fusion splices.
0.35
0.3
0.25 Connec tor
M e an Loss in 0.2
Mec hanic al Splice
dB 0.15
0.1 Fus ion Splice
0.05
0
1
Figure 3: Typical attenuation (mean loss) in dB
The single-mode fiber attenuation in Table 1 shows typical losses for cables and patches.
Table 1: Single-Mode Fiber Attenuation
Description Attenuation
Patch cords 0.20 - 0.22 (dB per km)
Indoor cables 0.23 - 0.27 (dB per km)
Outdoor cables 0.22 - 0.26 (dB per km)
Main trunk (duct) 0.21 - 0.25 (dB per km)
Aged fiber (estimate) 0.30 (dB per km)
Connec t or 0.30 dB
Mechanical splice 0.15 dB
Fusion splice 0.05 dB
6 Application Notes - Data Replication Manager Using Very Long Distance GBICs
Examples of Fiber Link Budgets
Examples of Fiber Link Budgets
The following two examples demonstrate how to calculate the link power budget for the Compaq
SANworks Very Long Distance GBICs. The first example demonstrates a workable fiber line; the
second describes a fiber link that will not work.
Link power used for calculations has a minimum value of 24 dB. Calculations are performed for one
direction in a bidirectional link.
Example 1
Company A wants to set up a 70 kilometer link from their local data center to a remote site. Their link
power budget is 24 dB.
Their link will have the following parameters:
A high-quality fiber with an attenuation of 0.21 dB per kilometer. This is equal to 0.21 dB x 70
km, or 14.7 dB of attenuation or signal loss.
One fusion splice every 5 kilometers: 0.05 dB x 14 fusion splices is equal to 0.7 dB of
attenuation.
Six connectors at 0.3 dB of loss per connector: 0.3 dB x 6 connectors is equal to 1.8 dB of
attenuation.
One mechanical splice at 0.15 dB of attenuation.
One 0.5 kilometer length of indoor cable at 0.23 dB of attenuation per kilometer. This is equal
to 0.23 dB x 0.5 (half a kilometer), which is 0.115 dB of loss.
Summing up the total loss:
14.7 dB fiber attenuation
0.7 dB fusion splices
1.8 dB connector attenuation
0.15 dB mechanical splice
0.115 dB indoor cable loss
--- ----- --
17.465 dB Total Loss
Total Link Power Budget minus Total Loss: 24 dB - 17.465 dB = 6.535 dB.
The margin of 6.535 dB indicates that this is a workable fiber link.
Example 2
Company B wants to set up a 70 kilometer link from their local data center to a remote site. Their link
power budget is 24 dB.
Their link will have the following parameters:
Average quality fiber with a 0.3 dB per kilometer attenuation rate: 0.3 dB x 70 km is equal to
21 dB of attenuation.
One fusion splice every 5 kilometers: 0.05 dB x 14 fusion splices is equal to 0.7 dB of
attenuation.
Twenty connectors at 0.3 dB of loss per connector: 0.3 dB x 20 connectors is equal to 6.0 dB
of attenuation.
Application Notes - Data Replication Manager Using Very Long Distance GBICs 7
Examples of Fiber Link Budgets
Five mechanical splices at 0.15 dB of attenuation per mechanical splice is equal to 0.75 dB of
loss.
Two 0.5 kilometer lengths of indoor cable at 0.23 dB of attenuation per kilometer. This is
equal to 0.23 dB of attenuation loss.
Summing up the total loss;
21.0 dB of fiber attenuation
0.7 dB fusion splices
6.0 dB connector attenuation
0.75 dB mechanical splice
0.23 dB indoor cable loss
--- ----- --
28.68 dB Total Loss
This total loss is greater than the 24 dB link power budget; the fiber link will not work.
For Company B to resolve this issue, it must reduce the number of connectors, change the mechanical
splices to fusion splices, and invest in a higher quality fiber cable. Table 2 shows the implications of
configuration elements.
Table 2: Configuration Restrictions and Recommendations
Restrictions and Recommendations Implication
Use low-attenuation 9-micron fiber. Best for long distances (preferably less than 0.3 dB per km).
Minimize connectors. Connectors account for 0.3 dB, or greater, of signal loss.
Use fusion splices. Minimizes attenuation.
For fibers, from any point of the optical link, Exceeding the bend radius can result in fracture of the fiber.
minimum bending radius is 3.1 inch during
installation and 2.0 inch long-term.
During installation, avoid extreme Avoids possible damage to the fiber cable.
environments, such as excessive temperature
and vibration.
During installation, ensure that the fiber cable Prevents compression and stretch to the fiber cable.
is not pinched or pulled.
Use measurement tools such as calibrated Verifies optical link losses.
light sources, power meters, and an optical
time domain reflectometer (OTDR).
8 Application Notes - Data Replication Manager Using Very Long Distance GBICs
Ordering Compaq SANworks Very Long Distance GBICs
Ordering Compaq SANworks Very Long Distance GBICs
Contact your local Compaq representative to order the following kit:
Kit number: 230800-B21
Description: GBIC-VLD Connector Kit ALL
Laser Safety Compliance
The Compaq SANworks Very Long Distance GBIC is an international Class 1 laser product under
IEC825. The GBIC-VLD Module contains a laser device. All Compaq systems equipped with a laser
device comply with safety standards, including International Electrotechnical Commission
EN60825-1:1994+A11 and EN608252:1994. With specific regard to the laser, the equipment complies
with laser product performance standards set by government agencies as a Class 1 laser product. The
product does not emit hazardous laser radiation. The Center for Devices and Radiological Health
(CDRH) of the U.S. Food and Drug Administration implemented regulations for laser products on
August 2, 1976. These regulations apply to laser products manufactured from August 1, 1976.
Compliance is mandatory for products marketed in the United States. This device is classified as a
Class 1 laser product as defined by 21 CFR 1040.10.
The following label or equivalent is located on the surface of the unit:
This product is a Class 1 Laser Product.
This label indicates that the product is classified as a Class 1 laser product; Laserklasse 1.
Website
Check the Compaq website for more information on the complete line of Fibre Channel storage
products, product certification, technical information, updates, and documentation. This information
can be accessed through our web page at:
http://www.compaq.com/storage/san-mgmt
Application Notes - Data Replication Manager Using Very Long Distance GBICs 9
| 230800-B21
EK-DRMLD-AA
|
