STORAGE BASICS

What are the storage option available for a ESXi  host?

 Local SAS/SATA/SCSI storage

 Fibre Channel

 Fibre Channel over Ethernet (FCoE)

 iSCSI using software and hardware initiators

 NAS (specifically, NFS)

 InfiniBand

Other than Local Storage, how we can boot ESXi host?

Booting from Fibre Channel/iSCSI SAN

Network-based boot methods like vSphere Auto Deploy

USB boot

What is SAN?

A storage area network (SAN) is a dedicated network that provides access to consolidated, block level data storage. SAN refers to a network topology, not a connection Protocol.

What is fiber channel or FC?

Fibre Channel, or FC, is a high-speed network technology primarily used to connect computer and data storage devices and for interconnecting storage controllers and drives.

Fibre Channel is three times as fast as Small Computer System Interface (SCSI) as the transmission interface between servers and clustered storage devices.

Fibre channel is more flexible; devices can be as far as ten kilometers (about six miles) apart if optical fiber is used as the physical medium.

Optical fiber is not required for shorter distances; however, because Fibre Channel also works using coaxial cable and ordinary telephone twisted pair you can use it in shorter distances.

The Fibre Channel protocol can operate in three modes: point-to-point (FC-P2P), arbitrated loop (FC-AL), and switched (FC-SW). Point-to-point and arbitrated loop are rarely used today for host connectivity, and they generally predate the existence of Fibre Channel switches.

What is SAN, NAS, DAS?

N A S- Network Attached Storage (File level storage) [ex-SMB, NFS]

D A S- Direct Attached Storage (Block level storage) [SATA, PATA]

S A N- Storage Area Network (Block level storage area network)                                                                [ISCSI, FCOE]            What is “World Wide Port No” or “World Wide Node No”?

All the objects (initiators, targets, and LUNs) on a Fibre Channel SAN are identified by a unique 64-bit identifier called a worldwide name (WWN). WWNs can be worldwide port names (a port on a switch) or node names (a port on an endpoint). For anyone unfamiliar with Fibre Channel, this concept is simple. It’s the same technique as Media Access Control (MAC) addresses on Ethernet.

50:00:00:25:b5:01:00:00 20:00:00:25:b5:01:00:0f

Like Ethernet MAC addresses, WWNs have a structure. The most significant two bytes are used by the vendor (the four hexadecimal characters starting on the left) and are unique to the vendor, so there is a pattern for QLogic or Emulex HBAs or array vendors. In the previous example, these are Cisco CNAs connected to an EMC Symmetrix VMAX storage array.  

 How different is FCoE from FC?

Aside from discussions of the physical media (Eathernet) and topologies, the concepts for FCoE are almost identical to those of Fibre Channel. This is because FCoE was designed to be seamlessly inter-operable with existing Fiber Channel–based SANs.    

What is VSAN?

Like VLANs, VSANs provide isolation between multiple logical SANs that exist on a common physical platform. This enables SAN administrators greater flexibility and another layer of separation in addition to zoning.          

What is Zoning? Why it is required?

 It ensures that a LUN that is required to be visible to multiple hosts with common visibility needs in a cluster is visible, while the rest of the host in the cluster that should not have visibility to that LUN do not.

 To create fault and error domains on the SAN fabric, where noise, chatter, and errors are not transmitted to all the initiators/targets attached to the switch. Again, it’s somewhat analogous to one of the uses of VLANs to partition very dense Ethernet switches into broadcast domains.      
  
How do you configure ‘Zoing’ in ‘FC’? What are the types of ‘Zoning’ you can configure in FC?

Zoning is configured on the Fibre Channel switches via simple GUIs or CLI tools and can be configured by (I) Port or by (II) WWN:

 Using port-based zoning:- Using port-based zoning, you would zone by configuring your Fibre Channel switch for example “put port 5 and port 10 into a zone that we’ll call zone_5_10.” Any device (and therefore any WWN) you physically plug into port 5 could communicate only to a device (or WWN) physically plugged into port 10.

 Using WWN-based zoning:- Using WWN-based zoning, you would zone by configuring your Fibre Channel switch to “put WWN from this HBA and these array ports into a zone we’ll call ESXi_4_host1_CX_SPA_0.” In this case, if you moved the cables, the zones would move to the ports with the matching WWNs.                                           

Initiator No +Fc Switch Port No + Network Address Authority Identifier=LUN No

What Is LUN Masking?

Zoning should not be confused with LUN masking. Masking is the ability of a host or an array to intentionally ignore WWNs that it can actively see (in other words, that are zoned to it).

Masking is used to further limit what LUNs are presented to a host

What is FCoE?

FCoE was designed to be interoperable and compatible with Fiber Channel. In fact, the FCoE standard is maintained by the same T11 body as Fiber Channel. At the upper layers of the protocol stacks, Fiber Channel and FCoE look identical. It’s at the lower levels of the stack that the protocols diverge.

In FCoE Fiber Channel frames are encapsulated into Ethernet frames, and transmitted in a lossless manner.

What is FCoE CNA’s?

In practice, the debate of iSCSI versus FCoE versus NFS on 10 Gb Ethernet infrastructure is not material. All FCoE adapters are converged adapters, referred to as converged network adapters (CNAs). They support native 10 GbE (and therefore also NFS and iSCSI) as well as FCoE simultaneously, and they appear in the ESXi host as multiple 10 GbE network adapters and multiple Fiber Channel adapters. If you have FCoE support, in effect you have it all. All protocol options are yours.

What is iSCSI?

iSCSI brings the idea of a block storage SAN to customers with no Fiber Channel infrastructure. iSCSI is an IETF standard for encapsulating SCSI control and data in TCP/IP packets, which in turn are encapsulated in Ethernet frames. The following shows how iSCSI is encapsulated in TCP/IP and Ethernet frames. TCP retransmission is used to handle dropped Ethernet frames or significant transmission errors. Storage traffic can be intense relative to most LAN traffic. This makes it important that you minimize retransmits, minimize dropped frames, and ensure that you have “betthe- business” Ethernet infrastructure when using iSCSI.

What is iSCSI Qualified Name?

An iSCSI qualified name (IQN) serves the purpose of the WWN in Fibre Channel SANs; it is the unique identifier for an iSCSI initiator, target, or LUN. The format of the IQN is based on the iSCSI IETF standard.

What is NFS?

NFS Stands for Network File System. NFS protocol is a standard originally developed by Sun Microsystems to enable remote systems to access a file system on another host as if it were locally attached. vSphere implements a client compliant with NFSv3 using TCP. When NFS datastores are used by vSphere, no local file system (such as VMFS) is used. The file system will be on the remote NFS server. This means that NFS datastores need to handle the same access control and file-locking requirements that vSphere delivers on block storage using the vSphere Virtual Machine File System, or VMFS. NFS servers accomplish this through traditional NFS file locks.

REMEMBER CAREFULLY:-

 (1) ESXi boot from SAN and (2) Raw device mapping (RDM) are not supported in NFS.