Wondering myself.

> On Apr 21, 2020, at 2:31 AM, Gionatan Danti <[email protected]> wrote:
> 
> 
> [reposting, as the previous one seems to be lost]
> 
> Hi all,
> I have a question regarding udev events when using iscsi disks.
> 
> By using "udevadm monitor" I can see that events are generated when I login 
> and logout from an iscsi portal/resource, creating/destroying the relative 
> links under /dev/

So running “udevadm monitor” on the initiator, you can see when a block device 
becomes available locally.   


> 
> However, I can not see anything when the remote machine simple 
> dies/reboots/disconnects: while "dmesg" shows the iscsi timeout expiring, I 
> don't see anything about a removed disk (and the links under /dev/ remains 
> unaltered, indeed). At the same time, when the remote machine and disk become 
> available again, no reconnection events happen.

As someone who has had an inordinate amount of experience with the iSCSi 
connection breaking ( power outage, Network switch dies,  wrong ethernet cable 
pulled, the target server machine hardware crashes, ...) in the middle of 
production, the more info the better.   Udev event triggers would help.   I 
wonder exactly how XenServer handles this as it itself seemed more resilient.  

XenServer host initiators  do something correct to recover and wonder how that 
compares to the normal iSCSi initiator.   

But unfortunately, XenServer LVM-over-iSCSi  does not pass the message along to 
its Linux virtual drives and VMs in the same way as Windows VMs.    

When the target drives became available again,   MS Windows virtual machines 
would gracefully recover on their own.    All Linux VM  filesystems went read 
only and those VM machines required forceful  rebooting.   mount remount would 
not work. 


> 
> I can read here that, years ago, a patch was in progress to give better 
> integration with udev when a device disconnects/reconnects. Did the patch got 
> merged? Or does the one I described above remain the expected behavior? Can 
> be changed?
> 
> Thanks.
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