[ClusterLabs] Antw: Re: OCFS2 on cLVM with node waiting for fencing timeout

[Eric Ren]

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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