As others have stated, it is indeed possible to forcibly import a disk group on more than one server simultaneously.
One other point - I/O fencing should protect you even in situations where outside servers are not using VCS or Volume Manager. Example: A server is being decommissioned and the disks are being wiped using a destructive analyze program. Unknown to anybody, one of the disks was also zoned to an active VCS server, which was using it (obviously a mistake, perhaps made many years before). An application on the VCS server goes down and has to be restored from backup, because the data was corrupted; the resulting outage lasted several hours, and some data was lost and not recoverable. If the VCS server had been using I/O fencing, the SCSI-3 reservation should have prevented the other server from accessing the disk. This is based on a situation I was directly involved in (and asked to find the root cause for). On Wed, Oct 13, 2010 at 2:44 PM, Everett Henson <ehen...@nyx.com> wrote: > Meant for this to go to the group... > > -----Original Message----- > From: Everett Henson > Sent: Wednesday, October 13, 2010 2:29 PM > To: 'A Darren Dunham' > Subject: RE: [Veritas-ha] I/O Fencing non-CFS > > Hmm. The consensus seems to be for Fencing in all cases where possible. I > got my first taste of VCS on version 3.5 before Fencing was an option and > I've never had to deal with it until a few months ago. > > My thanks to everyone for your replies. > > -----Original Message----- > From: veritas-ha-boun...@mailman.eng.auburn.edu [mailto: > veritas-ha-boun...@mailman.eng.auburn.edu] On Behalf Of A Darren Dunham > Sent: Wednesday, October 13, 2010 12:27 PM > To: veritas-ha@mailman.eng.auburn.edu > Subject: Re: [Veritas-ha] I/O Fencing non-CFS > > On Wed, Oct 13, 2010 at 11:39:30AM -0400, Everett Henson wrote: > > > Thanks Gene. I understand it's possible to import the group manually, > > but the discussion here was around how VCS would behave normally, > > without manual intervention. > > You're talking about a system designed to prevent problems in failure > situations. If everything is happy and healthy, it wouldn't be needed. > Older versions of VCS didn't have fencing and things worked okay most > of the time. > > > Wouldn't a vxdg -C to clear the private region give the server > > with the group already imported heartburn? Would it allow both > > servers simultaneous access to the storage? > > Both servers will assume they have exclusive control over the data and > will begin writing information. Yes, eventually the first server will > run into problems, but possibly not before corrupting the filesystem > and/or the disk group. I did some tests like this (*years* ago) and > managed to end up with a disk group that I couldn't import. > > > BTW, We are using two private interconnects as well as a link-lowpri > already. > > As long as the cluster is healthy and you don't have split-brain, then > it won't try to import on two. The fencing is more robust in those > situations where things are unhealthy. > > -- > Darren > _______________________________________________ > Veritas-ha maillist - Veritas-ha@mailman.eng.auburn.edu > http://mailman.eng.auburn.edu/mailman/listinfo/veritas-ha > Please consider the environment before printing this email. > > Visit our website at http://www.nyse.com > > **************************************************** > > Note: The information contained in this message and any attachment to it > is privileged, confidential and protected from disclosure. If the reader of > this message is not the intended recipient, or an employee or agent > responsible for delivering this message to the intended recipient, you are > hereby notified that any dissemination, distribution or copying of this > communication is strictly prohibited. If you have received this > communication in error, please notify the sender immediately by replying to > the message, and please delete it from your system. Thank you. NYSE > Euronext. > > _______________________________________________ > Veritas-ha maillist - Veritas-ha@mailman.eng.auburn.edu > http://mailman.eng.auburn.edu/mailman/listinfo/veritas-ha >
_______________________________________________ Veritas-ha maillist - Veritas-ha@mailman.eng.auburn.edu http://mailman.eng.auburn.edu/mailman/listinfo/veritas-ha
