Quick, Concise, and Useful Guide to Systems Administration and Engineering
Storage Area Networks (SANs)
General Concepts
iSCSI is an IP protocol that works over the TCP/IP network.
The clients reading from the iSCSI SAN are called initiators.
The chunks of storage presented by an iSCSI SAN to clients are called targets. One SAN can have multiple targets.
iSCSI is usually seen as a competitor to Fibre Channel (FC) which uses dedicated connections and switching which are pricey. In comparison, iSCSI operates over regular networks (e.g. switches and ethernet cabling).
One can have a software or hardware iSCSI initiator. In either case one is using the network, the difference is whether the regular network adapter is used for this purpose or a dedicated host bus adapter – which is essentially a network adapter with special capabilities that allow it to process iSCSI commands faster than a regular network card. It also reduces the load on the initiator’s CPU as it utilizes the HBA to perform necessary computations.
A LUN (logical unit number) is a portion of an iSCSI SAN which can be addressed specifically.
Ports Utilized: 860, 3260 (TCP)
The most common way to address a LUN is using its iSCSI Qualified Name (IQN), although Extended Unique Identifier (EUI) and T11 Network Address Authority (NAA) are sometimes used.
Internet Storage Name Service (iSNS) is a sort of DNS iSCSI initiators can use to discover iSCSI targets.
iSCSI SANs
Dell
Offers three series: SC, MD, and EqualLogic PS.
The SC Series is based on Dell’s acquisition of Compellent.
Switches
Brocade
Cisco
Emulex
QLogic
Connectors
SC Connector
LC Connector
Fiber
Single Mode
Multi Mode
Host Bus Adapter (HBA)
Software
Openfiler
metaSAN
XSan
StorNext
Red Hat GFS
VMWare VMFS
QFS
Metadata
Resources
Derrick Wlodarz. Windows Storage Spaces and ReFS: Is It Time to Ditch RAID for Good? BetaNews, 2014.