ChrisLopes
Contributor
Contributor

SAN Path

Hi,

Is the folloiwng setting recommended which is one active and the rest is ON?

What does the ON Means?

Is the above consider Active/Passive or Active/Active?

How does it look it if it is Active/Passive ?

How does it look it if it is Active/Active ?

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9 Replies
demz
Expert
Expert

Hi,

In VI3.5, the "ON" status is the VI3.0.x "standby" status.

With this view, you can't see if you're on an active/active SAN, look at your SAN documentation.

atbnet
Expert
Expert

Yes, "ON" means there is a link and the path is vaild to that LUN.

Agreed check SAN documentation. Most recently used (MRU) is mainly used for active/active SANs though I think, varies though san to san.

Andy, VMware Certified Professional (VCP),

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Andy Barnes
VCP / VCA-DT / MCITP:EA / CCIA
Help, Guides and How Tos... www.VMadmin.co.uk

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demz
Expert
Expert

The best practice for an active/active SAN is to use the "fixed" policy.

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java_cat33
Virtuoso
Virtuoso

If you select "Manage Paths" - it will display the policy being used.

If your current policy is "fixed" - and you haven't changed it manually....... your Storage controllers are running in a mode of active/active

If the policy is "most recently used (mru)" - then it's active/passive.

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atbnet
Expert
Expert

A check of my vmware manual says this:

Fixed:The ESX Server always used the preferred path to the disk when that path is available. If it cannot access the disk through the preffered path, then it tries the alternate paths. Fixed is the default for active/active devices.

MRU (Most Recently Used): The ESX Server use the most recent path to the disk until the path becomes unavailable. This is, the ESX Server does not automatically revert back to the original path. MRU is the default policy for active/passive storage devices and is required for those devices.

Manually changing between them is not recommended. The policy is set to what is required.

That should clear it up.

Andy, VMware Certified Professional (VCP),

If you found this information useful please award points using the buttons at the top of the page accordingly.

Andy Barnes
VCP / VCA-DT / MCITP:EA / CCIA
Help, Guides and How Tos... www.VMadmin.co.uk

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gtyrer
Contributor
Contributor

here is a url to a vmware document that gives you the recommended path policy for each SAN http://www.vmware.com/pdf/vi35_san_guide.pdf have a look at the OEM SAN Array Model Reference section

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ChrisLopes
Contributor
Contributor

Hi,

Based on above SAN Path Diagram, Let say if I have 5 blades server each with 2 HBA Card, Am I right to say that it will see 10 path. In the above diagram, it show 4 path because they are 2 balde server with 2 HBA Card on each blade? Is this statment correct?

I also read the guide that mention that it is 60s delay once the active path fail over to the Passive path.

Am I right to say that in 60s, nobody can access to the VM when the path failover occurs? Is this correct?

Thanks

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java_cat33
Virtuoso
Virtuoso

No that is incorrect.

Based upon the screenshot you attached, you have 2 x dual port hba's. The 4 paths you have are to your SAN lun. You have 2 paths per SAN controller.

If you have 5 blades each with 2 hba's, they will also only see 4 paths to the lun if your zoning and connectivity is the same as the host you took your screenshot from.

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ChrisLopes
Contributor
Contributor

Hi,

In what situation will it show the as " Standy" and in what situation will it show "On" for HBA Card based on the diagram below on the san path.

In addition, will the user able to use the VM assume the Fibre cable is plug out to ensure SAN Path redundancy?

Thanks for your patience

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