Hi,

On 10/13/2016 04:27 PM, Ulrich Windl wrote:
So I'm wondering why it takes so long to finish the fencing process?
As I wrote: Using SBD this is paranoia (as fencing doesn't report back a status like 
"completed" or "failed". Actually the fencing only needs a few seconds, but the 
timeout is 3 minutes. Only then the cluster believes that the node is down now (our servers boot so 
slowly that they are not up within three minutes, also). Why three minutes? Writing to a SCSI disk 
may be retried up to one minute, and reading may also be retried for a minute. So for a bad SBD 
disk (or some strange transport problem) it could take two minutes until the receiving SBD gets the 
fencing command. If the timeout is too low, resources could be restarted before the node was 
actually fenced, causing data corruption.
Good to know, but I am not familiar with SBD, so cannot comment on this.

Ulrich
P.S: One common case where our SAN disks seem slow is "Online" firmware update 
where a controller may be down 20 to 30 seconds. Multipathing is expected to switch to 
another controller within a few seconds. However the commands to test the disk in 
multipath are also SCSI commands that may hang for a while...
Thanks.

Eric

Eric
This was not expected for a cluster filesystem (by me).

I wonder: Is that expected bahavior?

Regards,
Ulrich



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