[stgt] help tgt segfault

[FUJITA Tomonori]

On Tue, 03 Feb 2009 10:57:22 +0100
Tomasz Chmielewski <mangoo at wpkg.org> wrote:

> FUJITA Tomonori schrieb:
> > On Tue, 03 Feb 2009 10:36:22 +0100
> > Tomasz Chmielewski <mangoo at wpkg.org> wrote:
> > 
> >> FUJITA Tomonori schrieb:
> >>
> >>>> If you could provide me some "debug" version of tgtd, maybe?
> >>> The following message showed up _after_ the segfault, right?
> >>>
> >>> Did you see any message _before_ the segfault?
> >> Once again - I connected the initiator at about 10:27, started copying the files.
> >> Before the segfault there were messages below (this target has 3 connected initiators from
> >> 2 machines / IP addresses).
> >> Hope it helps, let me know if you need any more info.
> > 
> > Let me make sure about your configuration,
> > 
> > 1) send the output of `tgtadm --op show --mode target` before starting
> > copying the files.
> 
> Target 1: iqn.2006-08.net.syneticon:superthecus.backup   
>     System information:                                  
>         Driver: iscsi                                    
>         State: ready                                     
>     I_T nexus information:                               
>         I_T nexus: 2                                     
>             Initiator: iqn.2006-12.net.syneticon:server.backup1
>             Connection: 0                                      
>                 IP Address: 192.168.111.173                    
>     LUN information:                                           
>         LUN: 0                                                 
>             Type: controller                                   
>             SCSI ID: deadbeaf1:0                               
>             SCSI SN: beaf10                                    
>             Size: 0 MB                                         
>             Online: Yes                                        
>             Removable media: No                                
>             Backing store: No backing store                    
>         LUN: 1                                                 
>             Type: disk                                         
>             SCSI ID: deadbeaf1:1                               
>             SCSI SN: beaf11                                    
>             Size: 1480476 MB                                   
>             Online: Yes                                        
>             Removable media: No                                
>             Backing store: /dev/superthecus/backup             
>     Account information:                                       
>         backup                                                 
>     ACL information:                                           
>         192.168.111.173                                        
> Target 2: iqn.2007-02.net.syneticon:superthecus.backup1        
>     System information:                                        
>         Driver: iscsi                                          
>         State: ready                                           
>     I_T nexus information:                                     
>     LUN information:                                           
>         LUN: 0                                                 
>             Type: controller                                   
>             SCSI ID: deadbeaf2:0
>             SCSI SN: beaf20
>             Size: 0 MB
>             Online: Yes
>             Removable media: No
>             Backing store: No backing store
>         LUN: 1
>             Type: disk
>             SCSI ID: deadbeaf2:1
>             SCSI SN: beaf21
>             Size: 3221 MB
>             Online: Yes
>             Removable media: No
>             Backing store: /dev/superthecus/backup1
>     Account information:
>     ACL information:
>         ALL
> Target 3: iqn.2009-02.net.syneticon:superthecus.test
>     System information:
>         Driver: iscsi
>         State: ready
>     I_T nexus information:
>         I_T nexus: 1
>             Initiator: iqn.2006-08.net.syneticon:server.syn2
>             Connection: 0
>                 IP Address: 192.168.4.52
>     LUN information:
>         LUN: 0
>             Type: controller
>             SCSI ID: deadbeaf3:0
>             SCSI SN: beaf30
>             Size: 0 MB
>             Online: Yes
>             Removable media: No
>             Backing store: No backing store
>         LUN: 1
>             Type: disk
>             SCSI ID: deadbeaf3:1
>             SCSI SN: beaf31
>             Size: 2147 MB
>             Online: Yes
>             Removable media: No
>             Backing store: /dev/superthecus/test
>     Account information:
>     ACL information:
>         ALL

OK, the above output doesn't fit to your explanation but the output of
the next mail looks fine.


> > 2) you use slow network in this configuration, as you said before?
> 
> Yes.
> Slow connection is just 5 kB/s in both directions.
> It's easy to reproduce the problem this way.
> Slow link is the third target above.

So the connections between the target box and 192.168.4.52 are slow
while the connections between the target box and 192.168.111.173 is
not slow.

Right?


> > 3) All your bug reports about this problem happened in this
> > configuration? If not, please tell me about the other configuration.
> 
> In "real life" it happens under slightly different (more complex, harder to set up) conditions:
> - tgtd uses DRBD resource as the block device (backing store)
> - link is about 100 kB/s (writes; DRBD replication over a slow internet connection) and fast local HDD IO (reads)
> - when DRBD exchanges bitmaps with the remote peer, it suspends IO for several seconds

The problem might be related with TMF.


> - more targets configured, more initiators connected

Hmm, just with lots of initiators? Even with decent link speed and no
suspended I/Os?

I'm not sure about what 'more targets configured' mean.
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