Best Practice: How to correctly remove a LUN from an ESX host

I find this to be a very common topic that is not covered.  This is the best article from VMware that I have seen regarding what to look out for when removing storage from a vSphere Cluster or ESX host.

Yes, at first glance, you may be forgiven for thinking that this subject hardly warrants a blog post. But for those of you who have suffered the consequences of an All Paths Down (APD) condition, you'll know  why this is so important.

Let's recap on what APD actually is.

APD is when there are no longer any active paths to a storage device from the ESX, yet the ESX continues to try to access that device. When hostd tries to open a disk device, a number of commands such as read capacity and read requests to validate the partition table are sent. If the device is in APD, these commands will be retried until they time out. The problem is that hostd is responsible for a number of other tasks as well, not just opening devices. One task is ESX to vCenter communication, and if hostd is blocked waiting for a device to open, it may not respond in a timely enough fashion to these other tasks. One consequence is that you might observe your ESX hosts disconnecting from vCenter.

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