[Cluster-devel] fence_scsi - Configuration file

[Ryan O'Hara <rohara@redhat.com>]

On Mon, Aug 03, 2009 at 05:33:51PM +0200, Jan Friesse wrote:
> Ryan O'Hara napsal(a):
>> What happens if we list devices and have auto_detect set to 'on'? Will
>> we ignore the devices? With this auto_detect parameter, it seems that
>> it will have to be explicitly set to 'off' and devices will have to be
>> listed if we want to avoid auto-detect. Also, what happens if I set
>> auto_detect to 'off' and I don't list any devices?
>>
>
> autodetect set to "on" can have one of these two consequences:
> - Ignore listed device - read only global sections for parameters

^^ I think this is the most logical thing to do.

> - Ignore listed device but use per device parameters in case we will  
> find this device by old method - This is what is implemented now
> - Use merge of listed devices and autodetected device
>
> autodetect is by default off. When we not have config file, it will  
> become on. When no devices is listed -> we turn it on

Shouldn't auto_detect be default on? We want fence_scsi to work like
it does now unless it is configured otherwise. I was thinking ...

- If not config file exists, auto_detect is on.
- If a config file does exists and auto_detect is not defined to be
  off, auto_detect should default to on ... regardless of whether or
  not any devices are listed.

> I hope nobody will ever set autodetect to off and don't list any device,  
> but we can do two things:
> - Ignore this flag and use vgs (this is what code does now)
> - Do what user want -> no device fencing

If this evern happens, the node will not register with any
devices. There are two possible outcomes:

1. If a reservation already exists (being held by another node/key),
the node in question won't have write access to the device(s) since it
didn't register with anything.
2. If a reservation does not already exist, nothing changes and the
node is completely unprotected and there is no way to fence it.

I suppose there is a third case where the node is already registered,
so doing nothing is valid, but this is just pure luck.