iSCSI

最後更新: 2017-07-05

目錄

  • 介紹
  • open-iscsi
  • tgtd
  • iscsitarget

介紹

iscsi 的 initiator 一共有兩類:

  • (Dependent / Independent) hardware HBA(host bus adapters) initiator
  • software initiator

連接方式:

node ------> target         # Server share 出來的 Disk 叫 "target"

Server TCP Port:

3260/tcp

資源的名稱 - IQN(iSCSI Qualified Name) :

IQN - iSCSI Name - A worldwide unique name for identifying the node.

iqn.yyyy-mm.<reversed domain name>[:identifier];

iSCSI Alias

A more manageable name for an iSCSI device or port used instead of the iSCSI name.
 

iSCSI Multipathing

When transferring data between the host server and storage, the SAN uses a technique known as multipathing.

Multipathing allows you to have more than one physical path from the ESXi host to a LUN on a storage system.

Generally, a single path from a host to a LUN consists of an iSCSI adapter or NIC, switch ports, connecting cables, and the storage controller port.

If any component of the path fails, the host selects another available path for I/O. The process of detecting a failed path and switching to another is called path failover.

Discovery

A discovery session is part of the iSCSI protocol, and it returns the set of targets you can access on an iSCSI storage system. The two types of discovery available on ESXi are dynamic and static. Dynamic discovery obtains a list of accessible targets from the iSCSI storage system, while static discovery can only try to access one particular target by target name and address.

Storage System

[Active-active]

Allows access to the LUNs simultaneously through all the storage ports that are available without significant performance degradation.

[Active-passive]

[Asymmetrical]

Asymmetric Logical Unit Access
ALUA-complaint storage systems provide different levels of access per port.
ALUA allows hosts to determine the states of target ports and prioritize paths.

[Virtual port]

Allows access to all available LUNs through a single virtual port.
These are active-active storage devices,
but hide their multiple connections though a single port.
These storage systems handle port failover and connection balancing transparently.
 

Package:

  1. targetcli (LIO(http://linux-iscsi.org))
  2. open-iscsi (2011)(http://www.open-iscsi.org/)
  3. iscsitarget ( 較舊的 IET(iSCSI Enterprise Target))
  4. TGT (很舊的 Linux SCSI target framework 來)
  5. open-iscsi
  6. iscsitarget

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