Could not detect setting of sitpua for device naa.xxx. Error Not supported.

I recently received a question about the following message appearing in the VMkernel logs of an ESXi host:

2012-12-07T12:15:58.994Z cpu17:420151)ScsiDeviceIO: 6340: Could not detect setting of sitpua for device naa.xxx. Error Not supported.

So what does that mean? Firstly, it isn’t anything to be greatly concerned about. SITPUA, short for Single Initiator Thin Provisioning Unit Attention, is related to Out Of Space (OOS) conditions on Thin Provisioned LUNs. To ensure that an Out Of Space (OOS) warning is sent to just one host using the affected LUN,  the SITPUA bit in the Thin Provisioning Mode Page must be set to 1. If it is set to 0, all hosts with access to the OOS LUN is sent to all hosts.

Essentially, the bit makes it such that the ‘thin provisioning threshold exceeded’ warning is delivered either to a single initiator (bit set to 1) instead of being delivered to all initiators (bit set to 0). If it is delivered to all initiators, it will cause a warning storm in the vCenter events tab, i.e. duplicate warnings from all ESXi hosts sharing the affected datastore. The recommendation is to prevent this spam by having the device support the SITPUA bit in Thin Provisioning Mode Page.

This is beyond VMware’s control, but if you observe a flood of OOS warnings happening on multiple hosts from a single LUN that is OOS, then the solution to give to the vendor provider is documented here – support the SITPUA bit.

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4 thoughts on “Could not detect setting of sitpua for device naa.xxx. Error Not supported.

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  4. In case anyone else stumbles on this….. I was confused because I couldn’t find the SITPUA bit described in the T10 specs. Then Cormac pointed out that it is in SBC3-r24. I see in SBC3-r35 it is now the SITUA bit in the Logical Block Provisioning mode page.