Lets Design, Implement and do Administration of ESX3

Virtualization with VMWare Infrastructure 3.0

STORAGE-Advance Concepts

Posted by Preetam on March 18, 2007

For preparing VCP you first need to read the Exam Blue print available on vmware site, after going through it you would realize that one should go through

  1. Basic Administration Guide
  2. Server configuration Guide
  3. Resource Administration

All the above guides and additional guides are available at Vi3 Documents in PDF

Below are the contents from all three guide, they are actually few important concepts rather than entire text. This blog talks about storage.

STORAGE

TYPES OF STORAGE

  • Local
  • Fibre Channel (FC)
  • ISCSI (Hardware iniatiated)
  • ISCSI (software iniatiated)
  • NFS (NFS client is built-in into ESX server)

iSCSI

With iSCSI, SCSI storage cmds are send by VM to its VMDKs & are converted into TCP/IP protocol packets and transmitted to a remote device or target, that stores the virtual disk. ISCSI initiators are responsible for transporting SCSI requests between ESX Server and the target storage device on the IP Network.

There are two types of ISCSI initiators

1. Software based

2. Hardware based

Software based iSCSI initiators have a code built into VMKernel which carries out the transporting job, using software initiators, the ESX server connects to a LAN through an existing NIC card using network stacks, in short you can implement iSCSI without purchasing specialized hardware. You also need to open a firewall port by enabling the iSCSI software client service.

Hardware based iSCSI initiators requires HBA cards which are specialized to transport iSCSI cmds over LAN to the target. Currently ESX Server supports only Qlogic QLA4010 iSCSI HBA.

NB: ESX 3.0 does not support both types of initiators on single system.

Naming requirements:

IQN (iSCSI qualified name)

e.g. iqn.1998-01.com.mycompany:myserver

Format Template: iqn.<year-mo>.<reversed_domain_name>:<unique_name>

Discovery methods

Initiator discovers iSCSI targets by sending a sendtargets requested for specific target address.

Static: Only available for Hardware based iSCSI initiators, you can manually add additional targets or remove unneeded targets. If you remove a dynamically discovery static target, the target can be returned to the list the next time a rescan happens, the HBA is reset, or the system is rebooted.

Dynamic: to use this method enter the address of the target device so that the initiator can established a discovery session with this target. The target device then responds by forwarding a list of additional targets that the initiator is allowed to access.


iSCSI Security

Since iSCSI communications between initiator and target happens over TCP/IP stack, it is necessary to ensure security of the connection. ESX server supports CHAP that iSCSI initiators can use for authentication purposes.

You can’t store VM on IDE or SATA, but on SCSI,NAS or FC storage only.

VMs communicate with datastore (where vmdk is placed) using SCSI commands, SCSI commands are encapsulated into various protocols e.g. FC,iSCSI, NFS depending type of physical storage.

HBA Naming convention vmhba1:1:3:1, Hba card 1, on Storage processor 1, using LUN3 and partition 1. First 2 numbers can change but last will remain unchanged

Select a large LUN if you plan to create multiple virtual machines on it., if more space is needed you can increase the VMS volume at any time –up to 64 TB.

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