Thanks for the info.

One more question, I just looked through the iscsi.conf file and the README
but I do not see a setting for explicitly setting dm-multipath.  How do I
enable it?


Geoff Galitz
Blankenheim NRW, Deutschland

-----Original Message-----
From: [mailto:[EMAIL PROTECTED] On
Behalf Of Mike Christie
Sent: Montag, 23. Juni 2008 23:44
Subject: Re: iSCSI and filesystem error recovery

galitz wrote:
> I am evaluating iSCSI in our production environment and have a
> question.
> When I induce a failure by powering down the iSCSI target while there
> is active traffic and then restore the iSCSI target 5+ minutes later,
> the filesystem remains in read-only mode.  Fair enough, I see by
> reading the docs that anytime a filesystem error is generated the
> filesystem is made read-only.
> I can clear this by ummounting and then remounting the filesystem.  Is
> there a more elegant or a recommended way of restoring the filesystem
> to a read-write state once the iSCSI target has returned to service?
> Ideally we'd like this to be a transparent process.  Perhaps dm-
> multipath is what I need?

I think dm-multpath is best. But if you setup dm-multipath to eventually 
return IO errors to the layer above it, then you will have the same problem.

At the iscsi layer you can set node.session.timeo.replacement_timeout to 
a higher value and that is how long we will hold onto IO before failing 
it (default is 2 minutes). There is a bug in this code where we can only 
hold on to it for so long. I just did this patch against 269.2 which 
allows you to set the node.session.timeo.replacement_timeout to 0 which 
will hold onto the IO until we reconnect.

At the dm multipath layer you can set the no_path_retry to do the same 
thing. If you set this to queue it will hold onto IO forever or until 
the user intervenes.

But like I said if you get FS errors then you have to unmount and 
remount. If your questions was about that then there is nothing I can do.

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