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:
1.Data Routers
2.SAN Hubs
3.SAN Switches
4.Cables
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:
1. PORT_ID
2. wwpn
3. Porttype_Portmode
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
Storage System NAS SAN DAS Architectures:
It defines how servers are connected to the storage array units.Popular storage architecture variants – DAS, NAS, SAN, iSCSI
DAS (Direct Attached Storage) – Name given to storage system that is directly attached to the host system. This is the most common storage architecture
NAS (Network Attached Storage) and NAS devices are specialized file servers optimized for serving storage, using a routable protocol (TCP/IP) over a LAN
SAN (Storage Area Network) is a specialized network, a communication infrastructure that provides physical connections and a management layer, access to high performance and highly available storage subsystems using block storage protocols. SAN is made of specific devices, such as HBA (Host Bus Adapters) in the host server, front-end adapters that reside in storage array
iSCSI – Internet Small Computer System Interface is a storage protocol based on TCP/IP. It encapsulates SCSI commands into TCP/IP packets and delivers it reliably over IP networks
What does Rule of 16 say?
Rule of 16 says that if we have 16 or fewer servers using SAN(Storage Area Network) is an expensive solution.
In such cases using NAS(Network Attached Storage) and iSCSI based solutions will be beneficial.
What is a SAN ?
A storage area network (SAN) is a specialized high-speed network of storage devices and computer systems (also referred to as servers, hosts, or host servers).
Currently,most SANs use the Fibre Channel protocol.
A storage area network presents shared pools of storage devices to multiple servers.
Each server can access the storage as if it were directly attached to that server. The SAN makes it possible to move data between various storage devices, share data between multiple servers, and back up and restore data rapidly and efficiently.
In addition, a properly configured SAN provides robust security, which facilitates both disaster recovery and business continuance.
Components of a SAN can be grouped closely together in a single room or connected over long distances.
This makes SAN a feasible solution for businesses of any size: the SAN can grow easily with the business it supports.
What are the components of SAN(storage area network)?/List the SAN (storage area network)Components:-
SAN(storage area network)is made of the following components :
1. SAN Switches
2. Fabric
3. Connections:HBA(Host Bus Adapters and Controllers)
SAN Switches :
Specialized switches called SAN switches are at the heart of the typical SAN. Switches provide capabilities to match the number of host SAN connections to the number of connections provided by the storage array.Switches also provide path redundancy in the event of a path failure from host server to switch or from storage array to switch.
Fabric :
When one or more SAN switches are connected, a fabric is created.
The fabric is the actual network portion of the SAN. A special communications
protocol called Fibre Channel (FC) is used to communicate over the entire network. Multiple fabrics may be interconnected in a single SAN, and even for a simple SAN it is not unusual to be composed of two fabrics for redundancy.
Connections: HBA and Controllers :
Host servers and storage systems are connected to the SAN fabric through ports in the fabric. A host connects to a fabric port through a Host Bus Adapter (HBA), and the storage devices connect to fabric ports through their controllers.
Are servers homogenous in SAN environment?
No.Servers need not be homogenous in SAN environment.Each server may host numerous applications that require dedicated storage for applications processing.
How does a SAN(storage area network) work?
The SAN (storage area network) components interact as follows:
1. When a host wishes to access a storage device on the SAN, it sends out a blockbased access request for the storage device.
2. The request is accepted by the HBA for that host and is converted from its binary data form to the optical form required for transmission on the fiber optic cable.
3. At the same time, the request is “packaged” according to the rules of the Fibre Channel protocol.
4. The HBA transmits the request to the SAN.
5. Depending on which port is used by the HBA to connect to the fabric, one of the SAN switches receives the request and checks which storage device the host wants to access.From the host perspective, this appears to be a specific disk, but it is actually just a logical device that corresponds to some physical device on the SAN. It is up to the switch to determine which physical device has been made available to the host for its targeted logical device.
6. Once the switch has determined the appropriate physical device, it passes the request to the appropriate storage device.
What is a fibre channel protocol(FCP)?
Fibre Channel Protocol (FCP) is a transport protocol (similar to TCP used in IP networks) which predominantly transports SCSI(small computer system interface) commands over Fibre Channel networks.
What are the various layers of fibre channel protocol/fibre channel?
Fibre Channel is a layered protocol. It consists of 5 layers, namely:
1. FC0 The physical layer, which includes cables, fiber optics, connectors,pinouts etc.
2. FC1 The data link layer, which implements the 8b/10b encoding and decoding of signals.
3. FC2 The network layer, defined by the FC-PI-2 standard, consists of the core of Fibre Channel, and defines the main protocols.
4. FC3 The common services layer, a thin layer that could eventually implement functions like encryption or RAID.
5. FC4 The Protocol Mapping layer. Layer in which other protocols, such as SCSI, are encapsulated into an information unit for delivery to FC2.
What is FC-PH?
FC0, FC1, and FC2 are also known as FC-PH, the physical layers of fibre channel. Where does the fiber channel router operate?
Fibre Channel routers operate up to FC4 level (i.e. they are in fact SCSI routers), switches up to FC2, and hubs on FC0 only.
What are the various speed at which we use fibre channel products?
Fibre Channel products are available at 1 Gbit/s, 2 Gbit/s, 4 Gbit/s, 8 Gbit/s, 10 Gbit/s and 20 Gbit/s. Products based on the 1, 2, 4 and 8 Gbit/s standards should be interoperable, and backward compatible. The 10 Gbit/s standard (and 20 Gbit/s derivative), however, is not backward compatible with any of the slower speed devices, as it differs considerably on FC1 level (64b/66b encoding instead of 8b/10b encoding). 10Gb and 20Gb Fibre Channel is primarily deployed as a high-speed "stacking" interconnect to link multiple switches.
What is an iFCP?
iFCP (Internet Fibre Channel Protocol) is an emerging standard for extending Fibre channel storage networks across the Internet. iFCP provides a means of passing data to and from Fibre Channel storage devices in a local storage area network (SAN) or on the Internet using TCP/IP. TCP provides congestion control as well as error detection and recovery services. iFCP merges existing SCSI and Fibre Channel networks into the Internet. iFCP can either replace or be used in conjunction with existing Fibre Channel protocols, such as FCIP(Fibre Channel over IP).
Why is iFCP superior to FCIP?
iFCP addresses some problems that FCIP does not. For example, FCIP is a tunneling protocol that simply encapsulates Fibre Channel data and forwards it over a TCP/IP network as an extension of the existing Fibre Channel network. However, FCIP is only equipped to work within the Fibre Channel environment, while the storage industry trend is increasingly towards the Internet-based storage area network. Because iFCP gateways can either replace or complement existing Fibre Channel fabrics, iFCP can be used to facilitate migration from a Fibre Channel SAN to an IP SAN or a hybrid network.
What is SAN island?
SAN (Storage Area Network) island is a storage network that acts as an independent unit. It can be compared against a LAN where PC's are networked and as a single integrated unit. WAN or Wide Area Network is formed by connecting two or more LAN. SWAN is formed by combining LAN+SAN (using same components for both purposes).
Basic architecture of SAN : Storage Array (set of disks) connected via network fabric(switches) to End clients.
When a SAN acts as an independent functional unit serving specific purpose it becomes a SAN island. It is common in IT industries to have separate infrastructure for Mainframe system and opensource software(UNIX,LINUX,NT Windows, Windows Servers). In such cases SAN islands can be useful. SAN islands can also be used to serve different IT departments/business units within an organization that function as separate entities(virtual separation). SAN can be also used to share data across systems. This is very useful in case of disaster recovery
