Storage

FC SAN (Fiber Channel Storage Area Network)

iSCSI (Internet Small Computer System Interface)

NAS (Network Attached Storage)

VMFS (Virtual Machine File System)

Storage System – This is the hardware itself, which manages disks into logical units (RAID).

LUN – Logical Unit Number – A part of logical unit. One logical unit can consist of multiple LUNs (and usually does)

RAID, JBOD (Just a Bunch of Disks)*, Hot Spare, Parity**

SP – Storage Processor

WWN (World-Wide Name) – 64 Bit number, to which we can attach a label

Fabric – part of SAN storage, components which are part of one access path (serverport, switch, storage port)

HBA – Host Bus Adapter – the card which connects a host to the Fiber Channel network (SAN Switch)

A non-RAID disk architecture

**A parity bit is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd. Parity bits are used as the simplest form of error detecting code.

Basic concepts of storageStorage security – Which ESX host should see which LUN?

SAN Zoning – A method, which makes it possible to create logical groups containing WWN nodes over the physical Fabric Channel network; it is applied on the FC switch level; it is similar to VLANs used in Ethernet networks

LUN Masking – A method, which makes it possible to „hide” certain Luns from certain hosts; usually implemented on HBA level

FC / SAN Switch – The most important component of the FC network, the HBAs can be connected to the SAN switch

Storage multipath

Storage multipath is a method which is vital in order to achive and maintain high availablity

Active/Active array (rarely used)

Active/Passive array (frequently used)

There are two types of multipathing policies in an ESX evironment:

Fixed – The ESX only uses the preferred path, path failover policy will only be used in case of failure.

MRU (Most Recently Used) : The path used most recently will be used in case of a failure, this is set by the ESX automatically. RoundRobin – Experimental only

This is automatically set by the ESX, but can be changed.