Re: [PATCH] dracut-module-setup: Return from iscsi path immediately for hardward iscsi without iBFT

[Minfei Huang]

On 09/25/15 at 02:39pm, Dave Young wrote:
>  On 09/24/15 at 01:29pm, Minfei Huang wrote:
>  > Hardware iscsi can export the iscsi device before starting to load the
>  > kernel code, which setups the iscsi card using the config stored in
>  > hardward iscsi card memory.
>  > 
>  > kdump need not do anything for this sort of hardware iscsi card, if this
>  > card does not have the feature iBFT. IBFT can export the iscsi
>  > configuration from hardware iscsi card memroy to current running kernel.
>  > Thus iscsiadm cann't get the iscsi session info using "iscsiadm -m
>  > session -r /sys/block/xxx", due to limitation of iscsi info exported by
>  > kernel.
>  > 
>  > Once the machine is plugged in this sort of hardware iscsi card, kdump
>  > returns as soon as possible.
>  
>  Since we do not know much about iscsi, could you describe the basic infomation
>  about them?
>  
>  1. how many type of cases we should consider for iscsi? 
There are three iscsi initiators we use more frequently.
1) software iscsi initiator
2) iSCSI HBA
3) iBFT

>  
>  2. what is the difference between them, how to diffrentiate them. 
1) software iscsi initiator
    - We can setup the iscsi environemnt by using tgt suit. It is more
    continent to setup the iscsi without the hardware supporting.

2) iSCSI HBA
    - System has no ability to detect the iscsi session config. The
    usage of exported iSCSI device is the same as local SCSI device.

3) iBFT
    - The iSCSI Bios Firmware Table (iBFT) is a table that is created in
    memory which is mapped with the iSCSI card firmware. Thus we can get
    the session config according to the command iscsiadm.
>  
>  3. how to setup them (basic steps) 
1) software iscsi initiator
    - According to the command iscsiadm to setup the available seesion,
    and the session info should be passed manually

2) iSCSI HBA
    - Do nothing, except for passing "rd.iscsi.firmware=1" to the
    kernel. The iSCSI device will use the config stored in firmware to
    setup the session.

3) iBFT
    - Pass "rd.iscsi.ibft=1" and "rd.iscsi.firmware=1" to the kernel
to
    setup the session. 

Thanks
Minfei