How is a SAN different from an ethernet network?
Both SAN and ethernet network use the same set of devices including switches, cables for connectivity.Ethernet network uses TCP/IP protocol.SAN uses fiber channel for transmission of data. Protocols popularly used by SAN switches are FCP(Fiber Channel Protocol), SCSI (Small Computer System Interface), iSCSI (Internet SCSI – SCSI+TCP)
What is a SAN?
SAN stands for Storage Area Network.It referes to set of storage devices attached to a LAN or an ethernet network.A network dedicated for the purpose of storage is referred to as a SAN
SAN Storage Area Network Components :
What are the major grouping of SAN(storage area network) components?
SAN(storage area network) components can be categorized under following three major categories:
1) Host Components
2) Fabric Components
3) Storage Components
Give details on host components:-
The host components of a SAN consist of the servers themselves and the components that enable the servers to be physically connected to the SAN:
1. Host bus adapters (HBAs) are located in the servers, along with a component that performs digital-to-optical signal conversion. Each host connects to the fabric ports from its HBA.
2. Cables connect the HBAs in the servers to the ports of the SAN fabric.
3. HBA drivers run on the servers to enable a server’s operating system to communicate with the HBA.
Give details on Fabric components:-
All hosts connect to the storage devices on the SAN through the fabric of the SAN.The actual network portion of the SAN is formed by the fabric components.The fabric components of the SAN can include any or all of the following:
Give details on data routers:-
Data routers provide intelligent bridges between the Fibre Channel devices in the SAN and the SCSI devices. Specifically, servers in the SAN can access SCSI disk or tape devices in the SAN through the data routers in the fabric layer.
What are SAN Hubs?
They are precursors to today’s SAN switches. A SAN hub connects Fibre Channel devices in a loop (called a Fibre Channel Arbitrated Loop, or FC-AL). Although some current SANs may still be based on fabrics formed by hubs, the most common use today for SAN hubs is for sharing tape devices, with SAN switches taking over the job of sharing disk arrays.
What are SAN Switches?
SAN switches are at the heart of most SANs. SAN Switches can connect both servers and storage devices, and thus provide the connection points for the fabric of the SAN.
What are modular switches?
For smaller SANs, the standard SAN switches are called modular switches and can typically support 8 or 16 ports (though some 32-port modular switches are beginning to emerge). Sometimes modular switches are interconnected to create a fault-tolerant fabric.
What are director-class switches?
For larger SAN fabrics, director-class switches provide a larger port capacity (64 to 128 ports per switch) and built-in fault tolerance.
How is a SAN topology defined?
The type of SAN switch, its design features, and its port capacity all contribute its overall capacity, performance, and fault tolerance. The number of switches, types of switches, and manner in which the switches are interconnected define the topology of the fabric.
What are Cables?
SAN cables are special fiber optic cables that are used to connect all of the fabric components. The type of SAN cable and the fiber optic signal determine the maximum distances between SAN components, and contribute to the total bandwidth rating of the SAN.
Give detailson Storage components:-
The storage components of the SAN are the disk storage arrays and the tape storage devices.Storage arrays (groups of multiple disk devices) are the typical SAN disk storage device. They can vary greatly in design, capacity, performance, and other features.Tape storage devices form the backbone of the SAN backup capabilities and processes.Smaller SANs may just use high-capacity tape drives. These tape drives vary in their transfer rates and storage capacities. A high-capacity tape drive may exist as a stand-alone drive, or it may be part of a tape library.A tape library consolidates one or more tape drives into a single enclosure.
Tapes can be inserted and removed from the tape drives in the library automatically with a robotic arm. Many tape libraries offer very large storage capacities—sometimes into the petabyte (PB) range. Typically, large SANs, or SANs with critical backup requirements, configure one or more tape libraries into their SAN.
Storage Area Network Port Naming,SAN Port Naming:
What is a SAN(storage area network) port?
The points of connection from devices to the various SAN components are called SAN ports.All ports in a SAN are fibre channel ports.
What is a fabric port?Fabric ports are the SAN ports that serve as connection points to the switches,hubs, or routers that comprise the fabric of the SAN.
What is a node?How many ports will a node have?
Each component in a SAN — each host, storage device, and fabric component (hub,router, or switch) — is called a node, and each node may have one or more ports defined for it.
What is port naming?
Port naming is an convention to identify the ports.Ports can be identified in a number of ways:
What is Port_ID?
Within the SAN, each port has a unique Port_ID that serves as the Fibre Channel address for the port. This enables routing of data through the SAN to that port.
What is a WWPN?
A unique World Wide Port Name (WWPN) identifies each port in a SAN. The WWPN is a globally unique identifier for the port that allows certain applications to access it from outside the SAN.
What is a Porttype_Portmode naming convention?
It is a port naming convention, the port name consists of the type of port it is (that is, on which type of SAN component the port is physically located) and how the port is used (its logical operating mode).Using that convention, the port’s name can change as it goes in and out of use on the SAN.
Give example of porttype_portmode:-
An unused port on a SAN Fibre Channel switch is initially referred to as a G_Port. If a host server is plugged into it, the port becomes a port into the fabric, so it becomes an F_Port. However, if the port is used instead to connect the switch to another switch (an inter-switch link), it becomes an E_Port.
Basic Layers in a SAN(Storage Area Network)/Basic SAN components are as follows :
1) Host layer
2) Switch layer/fabric layer
3) Storage layer
How do different components communicate in a SAN(storage area network)?
1) Server communicates with the switch and searches for a drive to access data from
2) Switch sends an acknowledgement to server and provides information on port used to access the disk drive. Switch also sends the protocol to be used for subsequent communication. It could be SCSI(Small Computer System Interface) or Fiber Channel Protocol
3) Now the server sends information to SCSI drives in the port specified by switch
4) SCSI drives communicate with the physical disk drives and they access the information
5) Now the server receives the information it needs
The system administrator needs to see the list of users who have logged in and out on their
machines and the times when they did so. What should they do?
The last command searches the /var/log/wtmp file and displays who has logged on to the machine and the time
What is the most likely cause of a Solaris Server with PowerPath handling when there is a path failure?
Host HBA TimeOutValue set to 0 causes failure
What happens during zone failure?
The host cannot see the FA but the node list shows the HBA and FA logged into the switch
What is the procedure to copy the active zone set from SAN Manger ?
There is a copy automatically created in planned zone sets and nothing more needs to be done
How is a SAN different from an ethernet network?