I/ fencing handles corner cases.
- Hung node returning after being excluded from cluster
- Network interconnects severed
I/ fencing provides 2 basic functions
- enhanced membership arbitration to determine who is in the cluster
- SCSI-III disk reservations to block access to disk, just in case
anything at all fails in overall membership arbitration
Message
From: veritas-ha-bounces (AT) mailman (DOT) eng.auburn.edu
[mailto:veritas-ha-bounces (AT) mailman (DOT) eng.auburn.edu] Behalf Jim
Senicka
Sent: Tuesday, September 19, 2006 11:25 AM
To: Steven Sim; veritas-ha (AT) mailman (DOT) eng.auburn.edu
Subject: Re: [Veritas-ha] low priority heartbeat vs I/ Fencing
EMC = 170 odd Gig disks.
Coordinator needs 3 10mb LUNS.
I waste more space than that on storing bad jokes from email
I/ fencing is best possible config to prevent split brain.
Low Priority is a best practice, but is still not bulletproof.
Message
From: Steven Sim [mailto:steven.sim (AT) faplccc (DOT) net]
Sent: Tuesday, September 19, 2006 11:18 AM
To: Jim Senicka; veritas-ha (AT) mailman (DOT) eng.auburn.edu
Subject: low priority heartbeat vs I/ Fencing
Hello Gurus;
Firstly, I wish to thank James Senicka of Symantec for his wonderfully
fast and very technically accurate replies.
I wish all other product vendors were so efficient.
Support like this is one reason why I will continue to push VCS as a
clustering solution.
I am currently trying to convince a customer to implement I/0 Fencing
with three SAN based co-ordinator disks.
I've told him 3 are required (minimum) and they cannot be used for data.
At which point he threw a look at me and asked me whether I was aware of
how much per byte his EMC was costing him.
Sosome bright spark suggested a low priority heartbeat. Which I was
going to implement anyway, with or without I/ Fencing.
My question is;
Is a low priority heartbeat sufficient for I/ Fencing? If so, why the
strong recommendation for I/ Fencing with three co-ordinator disks?
I have been telling people that a low priority heartbeat is not
sufficient protection against split brain scenarios. Could you guys
comment?
Warmest Regards
Steven Sim
Fujitsu Asia Pte. Ltd.
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