Revision as of 08:03, 11 August 2009

Definition

1. A network whose primary purpose is the transfer of data between computer systems and storage elements and among storage elements.

A SAN consists of a communication infrastructure, which provides physical connections, and a management layer, which organizes the connections, storage elements, and computer systems so that data transfer is secure and robust. The term SAN is usually (but not necessarily) identified with block I/O services rather than file access services.

2. A storage system consisting of storage elements, storage devices, computer systems, and/or appliances, plus all control software, communicating over a network.

The SNIA definition specifically does not identify the term SAN with Fibre Channel technology. When the term SAN is used in connection with Fibre Channel technology, use of a qualified phrase such as "Fibre Channel SAN" is encouraged. According to this definition, an Ethernet-based network whose primary purpose is to provide access to storage elements would be considered a SAN. SANs are sometimes also used for system interconnection in clusters.

• definition source Storage Networking Industry Association (SNIA) definition
• SNIA's] full definition of a SAN

See also

Network Attached Storage (NAS)

Differences between a SAN and a NAS

How the terms DAS NAS and SAN are used by the storage industri

A NAS is defined by SNIA as

systems that provide file services to host computers using file access protocols

A SAN is is defined by SNIA as

The term SAN is usually (but not necessarily) identified with block I/O services rather than file access services.

Conclusion

• A NAS can always be called a SAN
• A SAN can not necessarily be called a NAS unless it offers File Services via a network.

A NAS using a SAN backend

It is possible for a NAS to use a SAN backend as displayed in picture 2.

picture 2: A NAS with a SAN backend

Additional reading

• IP Storage White Paper by SNIA
• Storage Network Security by SNIA
• Storage virtualization by SNIA
• SNIA education WEB. Lots of god stuff

VSAN - Virtual SAN

Virtual SAN - minder om VLAN

Inter VSAN Routing IVR

IVR - Inter VSAN Routing - også kendt som Fabric Routing giver forbindelse mellem Fabrics uden at sammenkoble dem direkte.

• Giver separation mellem Fabrics hvis der sker fejl i den lokale SAN
• Kan dele data mellem tusindvis af enheder
• Deling af centrale enheder mellem flere SAN's (Backup centralt af flere SAN's)
• Enheder i flere VSAN's kan kommunikere
• Replikering af data mellem VSAN's. (Reducere trafik lokalt)

FSPF - Fabric Shortest Path First

• Path-selection Protokol anvendt af FC (Fibre Channel) - Som OSPF

FSPF supporterer

• Multipath Routing
• Anvender Dijkstra algoritmen (Som OSPF)
  • Dijkstra kører pr VSAN. (Som OSPF pr AREA)

Zoning

Zoning anvendes til at kontrollere forbindelse mellem Initiator og Storage Targets. Anvendes til at lave Access Control. Anvendes i et SAN eller et VSAN til at sikre hvilke enheder der kan se hvilke enheder.

Zoning eksempel

FICON

Fber Connectivity er en OSI øvrelag protokol udviklet af IBM og anvendes til at sammenkoble IBM mainframes med Control Units (Storage). FICON afløser den lidt ældre ESCON og har følgende fordele.

• Kører på gigabit Fibre Channel
• Protokollen har bedre flowcontrol end ESCON og kan anvendes over store fysiske afstande.
  • Op til 100 Km før der mærkes nedgang i performance mellem enhederne.

FICON eksempel

SANTap

SANTap er en facilitet der er supporteret på Cisco Storage Services Module (SSM) på MDS9500 og MDS9200 serie Fabric Directors. SANTap har følgende faciliteter

• Tillader transparent duplikering af data i Switch fabric.
• Kan for eksempel anvendes til samtidig backup

SANTap eksempel

designing SAN and SAN extension

Port density and Topology Requirements

En vigtig parameter ved designet af et SAN er antallet af porte. For eksempel vil et SAN med 100 porte være meget anderledes end et SAN med 1.500 porte. Stil disse spørgsmål før SAN'et designes

• Hvor mange porte er nødvendige nu?
• Hvor mange porte vil være nødvendige i fremtiden?
• Hvad er den forventede levetid af SAN'et

Best practice

• Design netværket for fremtiden, men installer kun det antal porte der er nødvendige nu.
• Beregn en overkapacitet fra Storage enhederne mod serverne i foholdet 7:1 til 15:1 (Afhængig af platforme og applikationer)

Vigtige SAN design faktorer

Simplificeret SAN management

Single-Switch Collapsed Core Design

Single-Switch Collapsed Core Design

Small-Scale, Dual-Fabric Collapsed Core Design

Medium and Large-Scale, Dual-Fabric Core-Egde Design

Medium-Scale, Dual-Fabric Core-Egde Design

Large-Scale, Dual-Fabric Core-Egde Design

SAN extension

SAN Extensions refererer til at transportere Storage trafik over MAN eller WAN's. SAN Extensions kan fx. køre over ISCSI.

SAN extension eksempel

SAN Extension protocols

For eksempel FCIP - Fiber Channel Over IP.

FCIP - Fiber Channel over IP

Eller ISCSI

ISCSI

I forbindelse med SAN extension kan benyttes

• Tape Acceleration: Nedsæt Remote backup tid.
• FCIP Write Acceleration: Gør I/O transaktioner mellem Servere og Storage Devices.
• Hardware-assisted Data Compresion over FCIP: Komprimer data over WAN-links.
• Hardware-based IPsec: Datasikkerhed

SAN extensions

SAN HIGH availability ala HSRP