a s p a s i a wrote:
> Hello all,
> 
> I have been wondering a given scenario, where a server boots linux
> over iscsiRoot;  how would iscsi initiator handle, if for instance,
> access to the iscsiRoot device is interrupted for a second or two.  A
> situation where this could possibly occur would be if one would add a
> new target in the /etc/ietd.conf in the iscsi-target host, and then do
> a restart, while certain hosts are booted against an iscsiRoot served
> by that same target.

This is what the replacement timeout is for. Section 8 in the README 
tries to describe how all those timers and scsi retries works. It is a 
little confusing, because some of the info on timeouts and retries is 
valuable for root and multipath but is only in the multipath section.

Each scsi command gets 5 retries. If you were to disrupt iscsi service 
by pulling cables or restarting targets then if the scsi command's 
execution gets disrupted more than 5 times you will get a error to the FS.

For each disruption you have replacement_timeout seconds to relogin to 
the target. If replacement_timeout expires then it does not matter how 
many scsi command retries you have left, the command will be failed and 
you will get an error to the FS.

You really really want to use dm-multipath with iscsi. With dm-multipath 
there are lots of fun settings for if all paths should fail or look like 
they have failed (for example if you reboot the target or pull cables).

> 
> Any thoughts?
> 
> Have there been any past discussions on this or any papers/techtips
> that may address this kind of situation?
> 

It has been discussed a lot on the list and that is why I tried to 
comment on it in the README. If you could read that and give me some 
feedback so it is more useful for others in the future it would be helpful.

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