[Pacemaker] i am very confused

Glory Smith xx2glory at gmail.com
Wed Feb 18 23:39:55 EST 2009

> The SBD mechanism ensures fencing through the shared disk. It can be
> used in combination with N nodes and OCFS2, for example.

yes i understand this. i want something like  , a node should be able to
reserve a share disk to do any IO . while this node is holding the
reservation other nodes should not be able to write any thing to that shared
disk. if a  node who has the reservation becomes errant , any other node
from cluster should come forward and remove the key of this errant node and
put it's own key to hold reservation. like this, we can prevent data
intigrity issue in better way.
i dont think i can achieve this through SBD . am i wrong??

> Uhm, that's exactly what scsi2reservation calls in the background.
> Though usually through a reboot, the other cluster members will have
> broken the reservation and restarted the services - after all, fail-over
> is the whole point of having an HA cluster.

do you mean scsi2reservation calls sg_persist?? Kindly confirm this.
After looking at it's code it seems to me it looks for scsi_reserve
command.  i tried to set scsi_reserve instance variable with
"/usr/bin/sg_persist"   to check whether it can take sg_persist command or
not. but i could not start the resource it always faild. .

> > 3)well regarding sfex , just saw it's document it seems i can use it for
> > general data store purpose.. does the ownership  does not gets effected
> > during reboots?
> Why would ownership information persist across reboots? That is
> non-sensical.
> SCSI2 reservations don't persist across reboots - the bus reset clears
> them.

That's why SCSI2 is not robust and i want persistent reservation.  if
ownership does not get affected during reboots we can properly control it
depending on package failover , abnormal failure etc.

> SBD is a stonith mechanism, so you must keep stonith-enabled=true.
> Sure you can mix them, but if you have node-level fencing, you don't
> need resource level fencing any longer.

so it means for sfex and scsi2reservation  i need to set stonith-enable
=false and for sbd i need to set stonith_enable= true.  The reason why i
want both is ,if we have both resource fencing and node fencing our soultion
will be more reliable.

Thanks a lot for your help,

> Regards,
>    Lars
> --
> Teamlead Kernel, SuSE Labs, Research and Development
> SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
> "Experience is the name everyone gives to their mistakes." -- Oscar Wilde
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