Solving reliability and scalability problems with iSCSI, part 2

The latest stable IET release, 0.4.15, suffers yet another misfeature: it will likely break all initiators when the ietd process is restarted (ietd restart, machine restart etc.).

This is because on ietd shutdown, the user space daemon is just killed, but it doesn’t have the corresponding signal handler and the kernel space module doesn’t perform any cleanups for it.

From initiator’s perspective, several things may happen:

  • the change will happen so fast that the initiator won’t notice anything
  • initiator will break the connection, but after reconnection, you will see your iSCSI drives remounted read-only, weird hangs etc.
  • initiator won’t be able to connect again

Of course, no one wants to have the filesystem remounted read only, or to have the hard drive ripped off from a working system (this is how it looks from the perspective of the kernel if we loose a iSCSI connection).

There is a simple solution to that, although some may say it’s an ugly hack.

Using iptables to block the traffic to and from the IET target just before it shuts down does the job – the change is trivial – in /etc/init.d/iscsi-target, add iptables lines as follows:

With it, and with changes described in part 1, your IET iSCSI target installation should be really bullet-proof.

Great! You’ve successfully signed up.

Welcome back! You've successfully signed in.

You've successfully subscribed to

Success! Check your email for magic link to sign-in.

Success! Your billing info has been updated.

Your billing was not updated.