The brand new vibrant nature out-of multipathing and you may failover necessitates the independency from handling and you will handling a keen ALUA TPG’s AAS

The reverse is true for TPG thereupon are, it’s AO having LUN dos and you can ANO to own LUN step 1.

Towards the some active/inactive ALUA-capable arrays, you can also find port communities that have “Standby” AAS unlike “ANO” for the low-proprietor SP.

Asymmetric Accessibility State

Ports in an ALUA TPG can be in the same AAS at all times with respect to a given LUN. The TPG’s AAS are reported to the initiators in response to the Statement TPGS command. The TPG descriptor is reported in byte 1 of that response.

Transitioning-This new TPG AAS is within the procedure of modifying in one county to some other. Including, if for example the SP out-of a keen AO TPG is being rebooted otherwise try removed offline, or if new SAN (storage space circle) admin yourself transmits LUN ownership (to the EMC CLARiiON, this really is known as trespass), the fresh new AAS of your TPG into the alternate SP change so you can AO. While this procedure try ongoing, the newest TPG AAS are transitioning.

While the TPG is in this state, receiving requests from the initiators return Hectic or a View Status with sense key Maybe not Able and ASC (additional sense code) Logical Tool Perhaps not Accessible or ASYMMETRIC Availableness State Changeover.

Standby-This state is similar to a passive SP in a non-ALUA configuration and on certain ALUA-capable arrays. It returns a See Position with sense key Not Able.

In the event that TPG is during which AAS, they aids a subset away from sales it allows if it is in AO AAS:

Unavailable-That it AAS is often viewed when the TPG’s the means to access the new LUN is restricted as a result of tools problems or other SCSI equipment constraints. A beneficial TPG inside county is unable to changeover in order to AO otherwise ANO till the error subsides.

ESXi six delivers brand new We/O in order to TPGs that are from inside the AO AAS, however, if they’re not offered, I/O is distributed to help you TPGs which might be in ANO AAS. If the shop selection gets suffered We/O to the TPGs which might be for the ANO AAS, the fresh assortment changes this new TPG’s condition so you can AO AAS. Which helps make you to definitely alter hinges on the latest ALUA management setting from the newest sites selection (understand the second part).

ALUA Management Modes

This is accomplished via a couple of purchases and answers so you’re able to and you can in the shop arrays. These requests are as follows:

Query-According to SPC-3, section 6.4.2, in response to this command, an array returns certain pages of the VPD (vital product data) or EVPD (extended vital product data). The inquiry data returned in response to this command includes the TPGS field. If the returned value in that field is nonzero, that device (LUN) supports ALUA. (See Table 6.3, later in this chapter, for the correlation between the value of the TPGS field and AAS management modes.)

Set Address Port Communities (Place TPGs)-This command requests that the storage array set the AAS of all ports in specified TPGs. For example, a TPG’s AAS can transition from ANO to AO via the Place TPGs command.

Table 6.step 1 ALUA AAS management modes

Not Supported-The response to the Report TPGs and Lay TPGs commands is invalid. This means that the storage array does not support ALUA or, in the case of EMC CLARiiON, the initiator records are not configured in a mode that supports ALUA.

Implicit-The array responds to Statement TPGs but not Set TPGs commands. In this case, setting the TPG’s AAS is done only by the storage array.

Explicit-The array responds to both Report TPGs and Set TPGs commands. In this case, setting the TPG’s AAS can be done only by the initiator.