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failover mode 1 for AIX
Hi All,
need a quick help.
We have change to upgrade the flare code of cx4 to 4.30
but there are 3 aix servers for which the failover mode is set to 1 where the emc recommended is 3.
i need a confirmation during the flare upgrade will the servers stay online? or
i need to change the failover mode to 3 before the code upgrade?
AnkitMehta
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November 15th, 2012 15:00
1. Compare actual host configuration against EMC e-Lab Support Matrix (ESM) http://elabadvisor.emc.com OR Check the Compatibility of the Host with FLARE here: https://elabnavigator.emc.com/do/navigator.jsp
2. I believe you must be using Powerpath on these servers. Hence, FailOver Mode 3. (Refer KB Article: emc99467)
Ideally, the Hosts should stay online during FLARE installation but you can verify the environment before committing the FLARE but as far as confirmation is concerned you would need to open a Service Request with the EMC Technical Support and get the hostgrabs analyzed but again it is advisable to First Change the Failover mode to Recommended setting (Refer KB Article: emc149420)and then Upgrade the FLARE.
AnkitMehta
1.4K Posts
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November 15th, 2012 16:00
Just to add further for Future References:
What is Failover?
Failover is the detection of an I/O Failure and the automatic transfer of the I/O to a backup I/O path.
Failover Modes
A CLARiiON array is an Active/Passive device and uses a LUN ownership model. In other words, when a LUN is bound it has a default owner, either SP-A or SP-B. I/O requests traveling to a port SP-A can only reach LUNs owned by SP-A and I/O requests traveling to a port on SP-B can only reach LUNs owned SP-B. It is necessary to have different failover methods because in certain situations a host will need to access a LUN on the non-owning SP.
Failover Mode 1 – Passive Not Ready Mode
In this mode of operation the non-owning SP will report that all non-owned LUNs exist and are available for access. Any I/O request that is made to the non-owning SP will be rejected. A Test Unit Ready (TUR) command sent to the non-owning SP will return with a status of device not ready. This mode is similar to Failover Mode 0 with Auto-Trespass disabled.
Note: This mode is most commonly used with PowerPath. To a host without PowerPath, and configured with Failover Mode 1, every passive path zoned, for example, a path to SP-B for a LUN owned by SP-A, will show to the server as Not Ready. This will show as with offline errors on a Solaris server, SC_DISK_ERR2 errors with sense bytes 0102, 0700, and 0403 on an AIX server or buffer to I/O errors on a Linux server. If PowerPath is installed, these types of messages should not occur.
Failover Mode 3 – Passive Always Ready Mode
In this mode of operation the non-owning SP will report that all non-owned LUNs exist and are available for access. Any I/O requests sent to the Non-owning SP will be rejected. This is similar to Failover Mode 1. However, any Test Unit Ready command sent from the server will return with a success message, even to the non-owning SP.
Note: This mode is only used on AIX servers under very specific configuration parameters and has been developed to better handle a CLARiiON non-disruptive upgrade (NDU) when AIX servers are attached.
Refer KB Article: emc157830 to understand Failover Modes in a detailed manner.
AnkitMehta
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November 15th, 2012 17:00
No Problem. Happy to help.
Jithu9288
61 Posts
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November 15th, 2012 17:00
thanks Ankit for the helpful information.
kelleg
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November 16th, 2012 14:00
Please remember to mark your question Answer and award points to the person providing the correct answer. It helps others looking for the same issue.
glen