Module 6: Storage Area Network - FC SAN (Introduction to SAN + Fibre Channel SAN) Flashcards
What are the benefits of SAN?
consolidate storage resources across multiple compute systems
centralizes management + improves utilization
enables connectivity across geographically dispersed locations
enables replication between storage systems
What is FC?
high speed network than runs on optical fiber cables and serial attached copper cables
provides high scalability
What are the speeds of FC?
1, 2, 4, 8, 16, 32, 64, and 128 Gb/s
What is the “fan out” ratio in a FC SAN environment?
ratio between a single port on a storage device and total number of servers attached to it
if fan out ratio is high and array becomes overloaded performance suffers
What is the “fan in” ratio in a FC SAN environment?
specifies accessiblity of a host port to multiple storage ports on multiple arrays
what are compute and storage systems referred to as in a FC SAN environment?
nodes - each node is source or destination of a FC frame
What does each node require in a FC SAN environment?
atleast one network adapter for physical communication interface between nodes
EX: HBAs, front end adapters
What are the most common cables used in FC?
optical fiber cables
Why would you use copper cables in an FC network?
for shorter distances since they provide good signal to noise ratio for distances 30m or less
How do optical cables carry data?
in the form of light
What are the two types of optical cables?
multimode
single mode
What is a multimode optical cable (MMF)?
multiple beams of light transmitted at different angles onto core of cable
What is a con of MMF cables?
multiple light beams in the cable tend to collide - weakens signal strength after certain distance - called modal dispersion
What is a single mode fiber cable (SMF)?
carries single ray of light that projects at center of core - limits modal dispersion
When do you typically use SMF?
long distance cable runs
distance dependent on power of laser and sensitivity of transceiver
What are the characteristics of a FC switch?
each node has dedicated communication path
provides fixed port count
active ports can be scaled up non-disruptively
some redundant components
What are the characteristics of a FC director?
high end switch w higher port count
has modular architecture
port count scaled up by adding blades or line cards
all components redundant/hot swappable
What are the ports in an FC SAN environment?
N Port
E Port
F Port
G Port
What is the N Port in an FC SAN?
node port - end point in a fabric - typically compute system port (FC HBA) or storage system port connected to switch
What is the E Port in a FC SAN?
port that forms connection between two FC Switches - known as expansion port - E Port connects to another E Port in the fabric ISLs
What is the F Port in a FC SAN?
port on a switch that connects to an N Port - also called fabric port
What is the G Port in a FC SAN?
generic (empty) port on switch that can be E or F port depending on functionality
How many layers are in the FC SAN Protocol stack?
FC-0 - FC-4
What is the FC-0 Layer?
physical layer - includes cables and physical paremeters - can be both electrical and optical media
What is the FC-1 Layer?
encode/decode layer - defines how data is encoded prior to transmission and decoded upon receipt
How is data encoded at the transmittor node in FC-1 Layer?
8 bit character encoded in 10 bit transmission character
character than transmitted to receiver node
What happens once character is transmitted to receiver node in FC SAN?
passed to FC-1 Layer which decodes to original 8 bit character
What bit length do FC links over 10GBs use?
64 bit to 66 bit transmission
What are FC Frame Delimiters?
identify the start and end of frame and primitive signal that indicates events at transmission port
What are three jobs that the FC-1 Layer performs?
FC Frame Delimiters
Link Initialization
Error Recovery
What is the FC-2 Layer?
routing/flow control layer - provides FC addressing structure and data organization
What is the FC-3 Layer?
common services layer - not implemented
What is the FC-4 Layer?
mapping interface layer - uppermost layer in stack
What is the job of the FC-4 Layer?
defines the app interfaces and way Upper Layer Protocols (ULPs - IP, NVMe etc.) are mapped to lower layers
What is a FC Frame?
fundamental transfer of data on the FC-2 Layer
What are the five part of a FC Frame?
start of frame (SOF) - 4bytes
frame header
data field
cyclic redundancy check (CRC) - 4 bytes
end of frame (EOF) - 4 bytes
What are the SOF and EOF in a FC frame?
act as delimiters
What is the frame header in a FC frame?
24 bytes long and contains addressing information for the frame
What is the data field in a FC frame?
contains data payload - up to 2112 bytes - most cases its SCSI data
What is the CRC in a FC frame?
checksum that facilitates error detection for frame content
What is a FC Address?
used for communication between nodes in a SAN
What is the main purpose of a FC Address?
to route data through the fabric
How big is a FC Address?
24 bits - assigned to N Ports during fabric login
What is a World Wide Name (WWN)?
unique 64 bit identifier - static to N Port on a FC network
similar to MAC address of NIC
What types of WWNs are used in a FC SAN?
World Wide Node Name (WWNN)
World Wide Port Name (WWPN)
both used to physically identify Nodes and Ports respectively
What are the 3 main SAN connection topologies?
DAS
FC-AL
FC-SW
What is a DAS FC SAN setup?
directly connecting host HBA to front end storage port - limited scalability
What is a FC-AL SAN setup?
fibre channel arbitrated loop
shared bandwidth hub that connect each host HBA to separate hub for redundancy
connects half of storage ports to one hub and the other half to the other hub
What are the advantages of FL-AL over DAS?
has more ports for scalability
What is FC-SW in a FC SAN?
fibre channel switched fabric - switching instead of shared hub
What is a disadvantage of FL-AL?
aging topology since its shared bandwidth
can only have one IO transfer at a time which can cause bottlenecking
has no zoning or security
What is zoning in a FC-SW environment?
allows us to create isolated/private conversations between ports
can create as many fan in or fan out ratios as you’d like
