On Fri, Jul 31, 2009 at 9:43 AM, Ulrich
Windl<ulrich.wi...@rz.uni-regensburg.de> wrote:
> On 30 Jul 2009 at 19:25, Erez Zilber wrote:
>> Mike,
>> I'm seeing some strange behavior that I don't completely understand:
>> during heavy IO, I disconnect the cable on the target machine and
>> after a few seconds, I'm trying to logout from that target on the
>> initiator side. Here's what I see:
> Hi,
> IMHO unpluggin the cable is a bad thing to test for network problems:
> 1) A Gb NIC typically takes up to 5 seconds to re-establish the link to a 
> switch
> after re-plugging.
> 2) The kernel (udev) may trigger the execution of some scripts to set up the
> network after un-plug/re-plug (maybe even using DHCP)
> 3) The TCP stack may suspend I/O until some timeout
> ...then come the iSCSI issues...
> Maybe a more effective (and easier to manage) test would be adding a blackhole
> route. That's purely software and it just makes the packets go to nowhere.

I'm not trying to test network problems. I'm trying to test real life
problems: a computer is connected in the lab and suddenly someone
pulls out the cable accidentally or the switch fails etc.


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