Tag Archives: flat

What’s New in Core Storage in vSphere 6.7 Part VI: Flat LUN ID Addressing Support

vSphere 6.7 core storage “what’s new” series:

A while back I wrote a blog post about LUN ID addressing and ESXi, which you can find here:

ESXi and the Missing LUNs: 256 or Higher

In  short, VMware only supported one mechanism of LUN ID addressing which is called “peripheral”. A different mechanism is generally encouraged by the SAM called “flat” especially for larger LUN IDs (like 256 and above). If a storage array used flat addressing, then ESXi would not see LUNs from that target. This is often why ESXi could not see LUN IDs greater than 255, as arrays would use flat addressing for LUN IDs that number or higher.

ESXi 6.7 adds support for flat addressing.  Continue reading What’s New in Core Storage in vSphere 6.7 Part VI: Flat LUN ID Addressing Support

ESXi and the Missing LUNs: 256 or Higher

A customer pinged me the other day and said they could not see a volume on their ESXi host. Running ESXi version 6.5. All of the normal stuff checked out, but the volume was nowhere to be seen. What gives? Well it turned out to be the LUN ID was over 255 and ESXi couldn’t see it. Let me explain.

The TLDR is ESXi does not support LUN IDs above 255 for your average device.

UPDATE (8/15/2017) I have been meaning to update this post for awhile. Here are the rules:

ESXi 6.5 does support LUN ID higher than 255, but only if those addresses are configured using peripheral LUN addressing. If your array uses flat addressing, it will not work (which is common for higher level LUN IDs).

ESXi 6.7 does now support flat LUN addressing so this problem goes away entirely.

See this post for more information on ESXi 6.7 flat support.

*It’s not actually aliens, it is perfectly normal SCSI you silly man.

Continue reading ESXi and the Missing LUNs: 256 or Higher