The dynamic characteristics of multipathing and failover requires the freedom of handling and managing an ALUA TPGa€™s AAS
The opposite holds true for TPG with this is actually, it really is AO for LUN 2 and ANO for LUN 1.
On some active/passive ALUA-capable arrays, you could discover interface teams with a€?Standbya€? AAS versus a€?ANOa€? regarding non-owner SP.
Asymmetric Access State
Ports in an ALUA TPG may be in identical AAS at all times with respect to certain LUN. The TPG’s AAS become reported into initiators in reaction on REPORT TPGS order. The TPG descriptor was reported in byte 1 of this reaction.
Transitioning-The TPG AAS is within the process of switching from 1 condition to another. For instance, if the SP of an AO TPG will be rebooted or perhaps is taken traditional, or if the SAN (closet network) admin by hand moves LUN possession (on EMC CLARiiON, this might be usually trespass), the AAS of this TPG from the alternative SP improvement to AO. Although this techniques was ongoing, the TPG AAS are transitioning.
Whilst the TPG is within this condition, obtaining demands from initiators go back ACTIVE or a CHECK PROBLEM with feeling essential never EAGER and ASC (additional good sense code) LOGICAL DEVICE never AVAILABLE or ASYMMETRIC ACCESSIBILITY COUNTY CHANGE.
Standby-This state is much like a passive SP in a non-ALUA setting and on particular ALUA-capable arrays. They comes back a CHECK STATE with good sense important NOT EAGER.
Whenever the TPG is during this AAS, it supporting a subset of instructions it takes when it is in AO AAS:
Unavailable-This AAS is usually viewed when the TPG’s use of the LUN is fixed because of hardware mistakes or any other SCSI device limits. A TPG within this condition cannot changeover to AO or ANO until the mistake subsides.
ESXi 6 sends the I/O to TPGs that are in AO AAS, however if they are certainly not available, I/O is sent to TPGs being in ANO AAS. When the storing selection obtains sustained I/O on TPGs being in ANO AAS, the range transitions the TPG’s state to AO AAS. Whom produces that modification varies according to the ALUA control setting regarding the space array (understand next section).
ALUA Management Settings
This is done via a couple of directions and replies to and from the storage space arrays. These directions are listed below:
INQUIRY-According to SPC-3, section 6.4.2, responding to this demand, a selection return some pages associated with VPD (vital goods data) or EVPD (offered vital item data). The query facts came back responding for this order contains the TPGS field. If returned advantages because area try nonzero, that tool (LUN) supporting ALUA. (See desk 6.3, later on within part, for correlation amongst the property value the TPGS field and AAS control modes.)
SET TARGET SLOT GROUPS (SET TPGs)-This order demands that the storing array ready the AAS of all harbors in given TPGs. For instance, a TPG’s AAS can transition from ANO to AO via the ready TPGs command.
Dining table 6.1 ALUA AAS administration modes
Not Supported-The response to the REPORT TPGs and ready TPGs directions is actually invalid. Therefore the storage collection doesn’t support ALUA or, in the case of EMC CLARiiON, the initiator reports commonly configured in a mode that helps ALUA.
Implicit-The selection reacts to REPORT TPGs however SET TPGs instructions. In cases like this, placing the TPG’s AAS is accomplished just by the storage array.
Explicit-The variety responds to both REPORT TPGs and SET TPGs commands. In such a case, place the TPG’s AAS is possible only of the initiator.