The ultimate story about OCR, OCRMIRROR and 2 storage boxes – Conclusion

Oct 15, 2009

This is a follow-up of chapter 5.
The most important thing in this story is the fact that it is perfectly possible to configure your Oracle RAC cluster with 2 storage boxes in a safe way. You just need an independent location for the 3rd voting disk, but if you have that, you can be sure that your cluster will remain running when one of those storage boxes fail. You will even be able to repair it without downtime after e.g. buying a new storage box (call Uptime for good prices…:)

So were all these tests then really needed? Yes, I do think so, because of the following reasons


The ultimate story about OCR, OCRMIRROR and 2 storage boxes – Chapter 5

Oct 12, 2009

Scenario 5: Loss of ocrmirror from non-ocr-master – reloaded

This is a follow-up of chapter 4.
In this final scenario, we do the same thing as in scenario 4. I.e. while crs is running on both nodes, we hide the ocrmirror from the non-ocr-master node, which is node 2 now.
So node 1 is the master, we hide ocrmirror from node 2 and we verify on node 2:

(nodeb01 /app/oracle/crs/log/nodeb01) $ dd if=/dev/oracle/ocrmirror of=/dev/null bs=64k count=1
dd: /dev/oracle/ocrmirror: open: I/O error

What happens?
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The ultimate story about OCR, OCRMIRROR and 2 storage boxes – Chapter 4

Oct 7, 2009

Scenario 4: Loss of ocrmirror from the non-OCR MASTER

This is a vollow-up of chapter 3.
Let’s try to do the same thing as scenario 3, however now hiding the lun from a node NOT being the OCR MASTER, while crs is running on both nodes.

What happens?
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The ultimate story about OCR, OCRMIRROR and 2 storage boxes – Chapter 3

Oct 2, 2009

Scenario 3: Loss of OCRmirror from the OCR MASTER only

This is a followup of chapter 2.

As we have seen in scenario 1, the OCR MASTER will update the votecount. Now let’s hide the ocrmirror from only 1 node: the node being the OCR MASTER, while the other node continues to see the ocrmirror. Will CRS get confused about this?

Note: while doing this test, crs is running on both nodes.
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The ultimate story about OCR, OCRMIRROR and 2 storage boxes – Chapter 2

Sep 19, 2009

Scenario 2: loss of ocrmirror, both nodes down

(This is the follow-up of chapter 1)

Let’s investigate the vote count a little further by doing the following test:

  • First stop crs on both nodes
  • Then make the lun with ocrmirror unavailable to both nodes

What happens?
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The ultimate story about OCR, OCRMIRROR and 2 storage boxes – Chapter 1

Sep 1, 2009

Scenario 1: loss of ocrmirror, both nodes up

(This is the followup of article “Introduction“)

Facts
  • CRS is running on all nodes
  • The storage box containing the OCRmirror is made unavailable to both hosts (simulating a crash of one storage box).

What happens?
Read the rest of this entry »


The ultimate story about OCR, OCRMIRROR and 2 storage boxes – Introduction

Aug 28, 2009

Some time ago I wrote a blog about stretched clusters and the OCR. The final conclusion at that time was that there was no easy way to get your OCR safe on both storages, and hence I disrecommended clusters with 2 storage boxes. However, after some more investigation I may have to change my mind. I did extended testing on the OCR and in this blog I want to share my experiences. Read the rest of this entry »


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