failover modes

it's a combination of different factors, flare version, PowerPath version..etc. This will get you started:

emc99467

Failover modes are set on per initiator bases, it can not be set on per LUN bases.

these two are good as well:

emc157830
emc166261

Very simply, failover mode 0 will allow an HBA to see a LUN only on the SP that owns the LUN.

Failover mode 1 will allow an HBA to see the LUN down both paths - this is why you need failover software like PowerPath when you select 1 for failover - it hides the other path.

regards,

glen kelley

That makes sence. Didn't know that.... *blush*

Glen,

i have a post in power path section with title "power path and HP-UX 10.20" and it is about handling two paths w/o PP.

Your comments will be appreciated.

can the fail over mode be changed to 1 from 0 online on a CX700/ 6.24.1 (5.0)

You can manually edit the registered initiators on an array, but why would you want to change the failover mode from 1 to 0 ? You will be losing functionality unless your host does not have any type of failover software and requires that change.

Without PowerPath (or any other failover software), you should always set the failover mode to 0 (zero). Then you should connect one HBA to SPA and the other HBA to SPB. At the LUN level, there is a setting called "auto-assignment". This was designed for systems without failover software on the server. When this is set to enable, if SPA fails, the LUN will auto-trespass to SPB.

This provides basic array failover protection.

Regards,

glen

From Primus (KnowledgeBase) article emc1818:

Auto-assign controls the ownership of a LUN when an SP fails in a storage system with two SPs. With Auto Assign enabled, if the SP that owns the LUN fails and the server tries to access that LUN through the second SP, the second SP assumes ownership of the LUN so the access can occur. The second SP continues to own the LUN until the failed SP is replaced and the storage system is powered up. Ownership of the LUN is then returned to its default owner.

If auto-assign is disabled in the previous situation, the other SP does not assume ownership of the LUN, so access to the LUN does not occur. A failover application such as ATF, PowerPath or PVLinks would assume responsibility for issuing the ownership change.

If you are running Application-Transparent Failover (ATF), PowerPath or Alternate Pathing (PVLINKs) on a UNIX server connected to the storage system, you must disable auto assign in order for ATF, PowerPath or PVLINKs to fail over LUNs to the working SP when the original owning SP fails.

You enable or disable auto assign for a LUN when you bind it. During the BIND operation, auto-assign is DISABLED by default on Fibre Channel arrays and ENABLED by default on SCSI-based arrays. You can also enable or disable this option after the LUN is bound without affecting the data or accessibility to the LUN.

The auto-assign property of a LUN can transfer control of a LUN from one SP to another. It is used in those rare configurations where no failover software is in place to perform a machine-initiated failover without operator intervention.

Allowing auto-assign to transfer ownership of a LUN from one SP to another can affect how the operating system accesses the LUN. Using this option would require the operator to make a system level change in order to access LUNs on the new device path.

Note: For HP-UX environments using Alternate Pathing, auto-assign will not enable PVLinks. You must enable auto-trespass using the appropriate methods described in the installation documentation.

i intended to ask chanhing from zero to 1.

here is my scenario.

I have fail over mode zero;Hp-UX(10.20) Vg with only one path now; both the HBAs are zoned but both paths are not visible as the fail over mode is zero.; no power path installed. Some LUN in the VG is currently owned by SPA and remianing by SPB. Both the HBAs are NOT zoned earlier; we just did recently and later noticed that the FOM is zero and not able to see the second/alternate paths.

We are planning to add the PVlinks(alternate/second path) to the VG so that host can switch the PV links in case one of the paths are lost or any of the SP fails. keeping FOM=1; I assume this ma work based on --"If auto-assign is disabled in the previous situation, the other SP does not assume ownership of the LUN, so access to the LUN does not occur. A failover application such as ATF, PowerPath or PVLinks would assume responsibility for issuing the ownership change" and my undestanding is with FOM=1 the auto assign/auto tresspass is disabled.

I did not really understood --"Note: For HP-UX environments using Alternate Pathing, auto-assign will not enable PVLinks. You must enable auto-trespass using the appropriate methods described in the installation documentation"

HP-UX with PVLinks requires a different setup - please see the Host Connectivity Guide for HP-UX:

Home > Support > Technical Documentation and Advisories > Host Connectivity/HBAs > Installation/Configuration

or

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/Technical_Documentation/300-000-614_a13_elccnt_0.pdf?mtcs=ZXZlbnRUeXBlPUttQ2xpY2tDb250ZW50RXZlbnQsZG9jdW1lbnRJZD0wOTAxNDA2NjgwMjZkYTczLG5hdmVOb2RlPVNvZndhcmVEb3dubG9hZHMtMg__

Also see KnowledgeBase article emc99467 and emc72897

glen

Please see KnowledgeBase articles emc127913 and emc133661 - these explain the DMP settings - it's different depending on which version of DMP you're using. Also, emc99467 for all hosts.

glen

Hi what is the suggested failover mode for unix machines with DMP veritas 3.2
I looked some where as 2 but we could see only 3 paths from the host to clariion when it is supposed to be 4.

When you right click on the Clariion and then choose connectivity status, are all 4 paths green instead of blue ?