TODO: Explain why I don't have iSCSI boot working yet, please

Target

File as a backstore this time 

  targetcli
  > /backstores/fileio/ create file_or_dev=/var/lib/libvirt/images/sunday.img name=sunday

Creating a target is easy 

  > /iscsi/ create

replace the default portal: 

  > cd /iscsi/your_target/tpg1/
  > portals/ create 172.19.12.1 3260
  > portals/172.19.12.1:3260 enable_iser boolean=true

Initiator

Discover targets at a given IP address

  iscsiadm --mode discoverydb --type sendtargets --portal 172.20.64.11 --discover

Login. Must use a node record id found by the discovery

  iscsiadm --mode node --targetname iqn.2014-08.rocks.narf.southpark --portal 172.20.64.11:3260 --login

https://www.thegeekdiary.com/iscsi-connection-command-examples-cheat-sheet/

List active sessions

  # iscsiadm -m session
  tcp: [1] 172.20.0.80:3260,1 iqn.2014-08.rocks.narf.southpark (non-flash)

The session number (sid) is the 1 in brackets.

Use iSER instead of TCP (initiator side)

If performance is poor, the initiator may have logged in using TCP instead of iSER. In my testing, to a ramdisk over IB, TCP got ~520 MiB/s, where with iSER I have gotten 3.2 GB/s.

You know you got TCP if dmesg describes your LUN like this: 

  [123.45678] scsi host1: iSCSI Initiator over TCP/IP
  [123.45678] scsi 1:0:0:0: Direct-Access     LIO-ORG  volume       4.0  PQ: 0 ANSI: 6

It should say iSER instead of TCP/IP. Log out of that session, then run this command. It also logs in, which makes me wonder if the initiator name argument above is necessary. 

  iscsi_discovery 172.20.64.13 -t iser -l

Now dmesg should show something more like this: 

  [123.45678] scsi host1: iSCSI Initiator over iSER
  [123.45678] scsi 1:0:0:0: Direct-Access     LIO-ORG  volume       4.0  PQ: 0 ANSI: 6

Rescan after the target adds a LUN

  # iscsiadm -m session --sid=1 --rescan
  Rescanning session [sid: 1, target: iqn.2014-08.rocks.narf.southpark, portal: 172.20.0.80,3260]

Log out when you're done (very, very carefully)

Just one specific target: 

  iscsiadm --mode node --target <IQN> --portal 192.0.2.* --logout

–portal seems to be optional.

All of the targets: 

  iscsiadm --mode node --logoutall=all