in-band(带内) and out-of-band(带外) management
在看IBM 一文档时发现了这篇文章，内容如下：
Requests and status information sent between a and the storage management station are managed in one of two ways: out-of-band or in-band. The way that you define your storage subsystem impacts the way that you configure your storage subsystem.
In-Band Management
In-Band Management sends requests and event information between a storage subsystem and the storage management station through the IO connections. The requests, event information, and user data are sent through the HBA or the iSCSI initiator to the controllers. The requests and event information are mixed with the user data. The host receives requests from the storage management station over the Ethernet and then sends the requests to the controllers through the I/O connections. The controllers also use the I/O connections to send event information to the storage management station through the host.
An access logical drive is necessary for in-band management. The access logical drive gives the requests and event information to the controller and to the storage management station.
Figure 2 In-Band Management
（1）、Ethernet Network
（2）、Users Sending and Receiving Data
（3）、Storage Management Station
（4）、Host
（5）、Host Bus Adapters (HBAs) or iSCSI Initiators
（6）、Controller A
（7）、Controller B
（8）、Controller Module Found in the Storage Subsystem
When you manually add storage subsystems, you need to give only the host name or IP address of one host. After the host is added, the host-agent software that runs on the host automatically finds any storage subsystems connected to the host.
Out-of-Band Management
The Out-of-Band Management method uses the Ethernet network. The Ethernet network sends requests and event information between a storage subsystem and the storage management station. The Ethernet isolates the user data from the requests and event information. User data is sent through the HBA or the Iscsi Initiator directly to the controller by using the IO connections.
Figure 1 Out-of-Band Management
（1）、Ethernet Network
（2）、Users Sending and Receiving Data
（3）、Storage Management Station
（4）、Host
（5）、Host Bus Adapters (HBAs) or iSCSI Initiators
（6）、Controller A
（7）、Controller B
（8）、Controller Module Found in the Storage Subsystem
（9）、Ethernet Cable from the controllers to the Ethernet Network
When you add storage subsystems by using this management method, you must give the of each controller in the storage subsystem. A DHCP server is recommended to manage the IP addresses for the parts of the storage subsystem.
Note:
A maximum of eight storage management stations can monitor an out-of-band-managed storage subsystem at the same time.
Out-of-band management offers the following advantages:
——There is no need for an access logical drive (unlike for in-band management). Therefore, you can use the maximum number of logical drives supported by the host servers’ operating system.
——If the I/O paths fail, you can still access the DS3000 storage subsystem out-of-band, check the status, and capture logs for effective troubleshooting. Access to both controllers is required for almost all in-band management functions.
——If in-band management cannot be used (for example, when the SMagent is not available for the host server operating system), you can effectively use out-of-band management.
We recommend setting up and using both methods, if at all possible. This will introduce some redundancy to your management setup and provide management access to the DS3000 subsystem even in the case of I/O path or Ethernet management network failure.