SAN Basic Fundamental

Fibreoptic cable:

Single mode:

glass fiber with a diameter of 8.3 to 10 microns that has one mode of transmission
_ Single-mode fiber (SMF) for longer distances

Multi-Mode cable

Common diameters in the 50-to-100 micron range for the light carry component
_ Multi-mode fiber (MMF) for shorter distances

World Wide Name

All Fibre Channel devices have a unique identity called the World Wide Name
(WWN). This is similar to the way all Ethernet cards have a unique Media Access
Control (MAC) address.
Each N_Port will have its own WWN
This WWN is a 64-bit address


Port address


The three Fibre Channel topologies are:
_ Point-to-point
_ Arbitrated loop
_ Switched fabric

Point-to-point

A point-to-point connection is the simplest topology
There is no sharing of
the media, which allows the devices to use the total bandwidth of the link
Fibre Channel is a full duplex protocol, which means both paths transmit data
Simultaneously

Arbitrated loop

Our second topology is Fibre Channel Arbitrated Loop (FC-AL).
FC-AL is more
useful for storage applications. It is a loop of up to 126 nodes (NL_Ports) that is
managed as a shared bus.

distance of up to 10 km is supported by the Fibre Channel

4.1.3 Switched fabric

It applies to switches and directors that
support the FC-SW standard, that is, it is not limited to switches as its name
suggests. A Fibre Channel fabric is one or more fabric switches in a single,
sometimes extended, configuration

Port types

E_Port: This is an expansion port. A port is designated an E_Port when it is
used as an inter-switch expansion port (ISL) to connect to the E_Port of
another switch, to enlarge the switch fabric

F_Port: This is a fabric port that is not loop capable. It is used to connect an
N_Port point-point to a switch.

FL_Port: This is a fabric port that is loop capable. It is used to connect an
NL_Port to the switch in a public loop configuration

G_Port: This is a generic port that can operate as either an E_Port or an
F_Port. A port is defined as a G_Port after it is connected but has not
received a response to loop initialization or has not yet completed the link
initialization procedure with the adjacent Fibre Channel device.

_ L_Port: This is a loop-capable node or switch port.

U_Port: This is a universal port—a more generic switch port than a G_Port. It
can operate as either an E_Port, F_Port, or FL_Port. A port is defined as a
U_Port when it is not connected or has not yet assumed a specific function in
the fabric

N_Port: This is a node port that is not loop capable. It is used to connect an
equipment port to the fabric.

N_Port: This is a node port that is not loop capable. It is used to connect an
equipment port to the fabric.

Domain ID

A domain ID is a unique number that identifies the switch or director to a fabric. It
can be either static or dynamic. Static (insistent) domain IDs are a requirement
for FICON. Each manufacturer will have a range of numbers, and a maximum
number of domain IDs that can be used in a fabric.


Fibre Channel Arbitrated Loop protocols

Initialize the loop and assign addresses
Arbitrate for access to the loop
Open a loop circuit with another port in the loop.
_ Close a loop circuit when two ports have completed their current use of the
loop.
Switch Switch
Switch
Mid-range UNIX
Windows
JBOD
Server
Windows
L_Port FL_Port
NL_Port NL_Port
E_Port
E_Port
E_Port
E_Port
F_Port F_Port G_Port
U_Port
N_Port N_Port
Workstation
not
yet completely
initialized
Private
loop device
Public
loop devic


Loop addressing

NL_Port, like an N_Port, has a 24-bit port address

Fibre Channel login


Port login

Port login, also known as PLOGI, is used to establish a session between two
N_Ports and is necessary before any upper level commands or operations can
be performed. During port login, two N_Ports (devices) swap service parameters
and make themselves known to each other.

Process login

Process login is also known as PRLI. Process login is used to set up the
environment between related processes on an originating N_Port and a
responding N_Port.

Fabric login

After the fabric-capable Fibre Channel device is attached to a fabric switch, it will
carry out a fabric login (FLOGI).

Spanning tree

In case of failure, it is important to consider having an alternative path between
source and destination available. This will allow data to still reach its destination.
However, having different paths available could lead to the delivery of frames
being out of the order, due to frame taking a different path and arriving earlier
than one of its predecessors

This means that switches keep to
certain paths, as the spanning tree protocol will block certain paths to produce a
simply connected active topology. Then the shortest path in terms of hops is
used to deliver the frames, and only one path is active at a time. This means that
all associated frames go over the same path to the destination. The paths that
are blocked can be held in reserve and used only if, for example, a primary path

Fabric shortest path first

Zoning:

Zoning allows for finer segmentation of the switched fabric. Zoning can be used
to instigate a barrier between different environments. Only the members of the
same zone can communicate within that zone and all other attempts from outside
are rejected.

Zoning can be implemented in two ways:
_ Hardware zoning
_ Software zoning

Hardware zoning

Hardware zoning is based on the physical fabric port number

The members of a
zone are physical ports on the fabric switch.

_ One-to-one
_ One-to-many
_ Many-to-many



storage devices that are zoned to port 1: ports 4 and 5.
Server B is also zoned so that it can only see from port 2 to port 6.
Server C is zoned so that it can see both ports 6 and 7, even though port 6 is
also a member of another zone.
A single port can also belong to multiple zones.


Software zoning

Software zoning is implemented by the fabric operating systems within the fabric
Switches
Node WWN
_ Port WWN

LUN masking


The term logical unit number (LUN) was originally used to represent the entity
within a SCSI target which executes I/Os


VSAN:


this gives the ability to
segment a single physical SAN fabric into many logical, independent SANs
About EMC Navisphere software

Navisphere Storage-System Initialization Utility

LUNs

A logical unit (LUN) is a grouping of one or more disks or disk
partitions into one span of disk storage space. A LUN looks like an
individual disk to the server’s operating system. It has a RAID type
and properties that define it.

If you need a LUN that exceeds the maximum number of disks for a RAID
type, or you need to expand the user capacity of an existing LUN, use the
metaLUN feature of Navisphere Manager (see Chapter 10, "Expanding LUN
Capacity With MetaLUNs"
RAID

RAID types

The RAID type of a LUN determines the type of redundancy, and
therefore, the data integrity provided by the LUN.

RAID 5 - A distributed parity array, which provides data integrity
using parity information that is stored on each disk in the LUN. This
RAID type is best suited for multiple applications that transfer
different amounts of data in most I/O operations

RAID 3 - A single-disk parity array, which provides data integrity
using parity information that is stored on one disk in the LUN. This
RAID type is best suited for single-task applications, such as video
storage, that transfer large amounts of data in most I/O operations

RAID 1 - A mirrored array, which provides data integrity by
mirroring (copying) its data onto another disk in the LUN. This RAID
type provides the greatest data integrity at the greatest cost in disk
space, and is well suited for an operating system disk.

RAID 1/0 - A mirrored individual access array without parity, which
provides the same individual access features as the RAID 5 type, but
with the highest data integrity. This RAID type is well suited to the
same applications as the RAID 5 type, but where data integrity is
more important than the cost of disk space.

RAID 0 - An individual access array without parity, which provides
the same access features as the RAID 5 type, but does not have parity
information. As a result, if any failure (including an unrecoverable
read error) occurs on a disk in the LUN, the information on the LUN

Disk - An individual disk type, which functions just like a standard
single disk, and, as such, does not have the data integrity provided by
parity or mirrored data. This RAID type is well suited for temporary
directories that are not critically important.
Hot Spare - A single global spare disk, which serves as a temporary
replacement for a failed disk in a RAID 5, 3, 1, or 1/0 LUN. Data from
the failed disk is reconstructed automatically on the hot spare. It is
reconstructed from the parity data or mirrored data on the working
disks in the LUN; therefore, the data on the LUN is always accessible.
A hot spare LUN cannot belong to a Storage Group

Number of disks you can use in RAID types
RAID type Number of disks you can use
RAID 5 3 - 16
RAID 3 5 or 9 (CX-Series or FC-Series)
RAID 1/0 2, 4, 6, 8, 10, 12, 14, 16
RAID 1 2
RAID 0 3 - 16
Disk 1
Hot Spare 1


Rebuild priority The rebuild priority is the relative importance of reconstructing data
on either a hot spare or a new disk that replaces a failed disk in a
LUN. It determines the amount of resources the SP devotes to
rebuilding instead of to normal I/O activity. Table 8-3 lists and
describes the rebuild time associated with each rebuild value.
The rebuild priorities correspond to the target times listed above. The
storage system attempts to rebuild the LUN in the target time or less.
The actual time to rebuild the LUN depends on the I/O workload,
the LUN size, and the LUN RAID type

Verify priority

The verify priority is the relative importance of checking parity
sectors in a LUN. If an SP detects parity inconsistencies, it starts a
background process to check all the parity sectors in the LUN

RAID group
Expansion

You can expand a RAID Group by adding one or more disks to it.
Expanding a RAID Group does not automatically increase the user
capacity of already bound LUNs. Instead, it distributes the capacity
of the LUNs equally across all the disks in the RAID Group, freeing
space for additional LUNs.

RAID group

Defragmentation

If you unbind and bind LUNs on a RAID Group, you may create gaps
in the contiguous space across the Group’s disks. This activity,
fragmenting the RAID Group, leaves you with less space for new
LUNs. You can defragment a RAID Group to compress these gaps
and provide more contiguous free space across the disks.
Defragmentation may also shorten file access time, since the disk
read/write heads need to travel less distance to reach data

Creating RAID groups

The table below lists the maximum number of RAID Groups allowed
per storage system based on storage system type:
To create a RAID
group
1. From the Storage tab of the Enterprise Storage dialog box,
navigate to the storage system on which you want to create a
RAID Group, right-click, and then select Create RAID Group.
2. In the Create RAID Group dialog box, select a RAID Group ID.
You cannot change the ID of the RAID Group without destroying the
RAID Group (and thus unbinding all its LUNs and losing their data) and
then recreating it with the new ID.
For a description of each property in the dialog box, click Help.
3. To create a RAID Group with disks and default values that
Manager selects, do the following:
a. Select automatic disk selection.
b. Select the number of disks that this RAID Group will contain.
c. Click Apply to create the RAID Group and close the dialog
box.
Manager creates the RAID Group with disks it selects, and sets
default values for the advanced properties.

CX700, CX600 CX500 CX400, CX300 CX200 CX200LC
240 120 60 30 2


Creating LUNs on RAID groups

Group.
For example, a RAID 5 RAID Group with five 9-Gbyte disks provides
36 Gbytes of user space and 9 Gbytes of parity data. If you bind one
2-Gbyte LUN, you will have 34 Gbytes left for additional LUNs. You
could bind 17 more 2-Gbyte LUNs using all the space in the RAID
Group, or you could bind four more 2-Gbyte LUNs and four 5-Gbyte

following table:
! CAUTION
Pre-FC4700 storage systems
Assign at least 2 Mbytes per RAID 3 LUN to the RAID 3 memory
partition. If this partition does not have adequate memory for the
LUN, you will not be able to bind it. Changing the size of the RAID
3 memory partition reboots the storage system. Rebooting restarts
the SPs in the storage system, which terminates all outstanding I/O
to the storage system.
CX-Series or FC4700-Series storage systems that support RAID 3
LUNs
Allocating the RAID 3 memory partition size is not required for
RAID 3 RAID Groups and LUNs (the RAID 3 memory partition
appears dimmed and is unavailable). If there will be a large
amount of sequential read access to this RAID 3 LUN, it may be
beneficial to enable read caching with prefetching for the LUN.
CX700 CX600, CX500 CX400, CX300
CX200,
CX200LC
2048 1024 512 256


When the bind operation is complete, use the following
Navisphere CLI command to determine which SP owns the
LUN.
navicli -h hostname getlun lun -owner
where
b. Start a background verify and set the sniffer rate for the LUN
with the following Navisphere CLI Command:
This step is not required for systems running storage system software
version 02.05 or later because background verifies are done
automatically.
navicli -h hostname setsniffer lun 1 -bv -bvtime ASAP -snrate
rate
where
hostname specifies the IP address or network
name of an SP in the storage system.
lun Specifies the logical unit number of the
LUN.
hostname specifies the IP address or network
name of an SP in the storage system.
lun Specifies the logical unit number of the
LUN.
rate Specifies the sniff rate. The rate you
should use varies with the capacity of
the disks in the LUN, as shown in the
table below. The default rate is 30.


NFS port no 2049
CIFS port no 445


MetaLUNs overview

The metaLUN
feature lets you dynamically expand the capacity of a single LUN
(base LUN) into a larger unit called a metaLUN

metaLUN in two ways

stripe expansion

stripe expansion takes the existing data
on the LUN or metaLUN you are expanding, and restripes
(redistributes) it across the existing LUNs and the new LUNs you are
Adding

stripe expansion

A stripe expansion takes the existing data
on the LUN or metaLUN you are expanding, and restripes
(redistributes) it across the existing LUNs and the new LUNs you are
adding. The stripe expansion may take a long time to complete

concatation expansion:

creates a new metaLUN component that
includes the new expansion LUNs, and appends this component to
the existing LUN or metaLUN as a single, separate, striped
component