- **status**: accepted --> review
---
** [tickets:#2259] amf: support for si-swap admin op for N+M model.**
**Status:** review
**Milestone:** 5.2.FC
**Created:** Wed Jan 11, 2017 06:13 AM UTC by Praveen
**Last Updated:** Mon Feb 20, 2017 08:59 AM UTC
**Owner:** Praveen
As per spec, SI_SWAP admin operation is applicable to a SI which is protected
by SG of 2N, NWAY or NPM model. Current OpenSAF implementation already supports
2N and N-WAY model.This enhancements is for supporting the admin operation on
SI of N+M model SG.
AMF B.04.01 spec writes about SI_SWAP armin operation for applicable red model
in the section "9.4.8 SA_AMF_ADMIN_SI_SWAP" page 386 of B.04.01 spec. For N+M
model, spec states that:
"If the designated SI is protected by a service group whose redundancy model is
N+M,
the invocation of this administrative operation results in a complete swap of
all active
and standby CSIs belonging to not just the designated SI but also to any other
SI that
is assigned active to a service unit to which the designated SI is assigned
active.
Application of this operation on an SI may potentially modify the standby
assignments
of other SIs that are protected by the same service group, but are not assigned
to the
service unit to which the SI in question is assigned active."
**Example configuration N+1 given in spec:**
In the same paragraph above in section 9.4.8 SA_AMF_ADMIN_SI_SWAP, one example
is given how SI_SWAP will proceed in N+M model.
1) Four nodes U, V, W and X hosts S1, S2, S3 and S4 respectively.
2) There are three SIs SIA, SIB and SIC.
3) SIA is active in S1, SIB is active in S2 and SIC is active in S3.
4) All SIs are standby in S4.
5) SI_SWAP admin operation Flow for above configuration: As per spec ,
"If the swap operation is applied on SI A, the active assignment
for SI A shall be moved to Service Unit S4 on Node X, and the standby
assignments
for SI A as well as that of SI C and SI B will be moved to Service Unit S1 on
Node U. The active assignments of SI C and SI B will remain on Service Unit S3
(on
Node W) and Service Unit S2 (on Node V), respectively"
Here SU S1 will become quiesced for all active SIs (only one SIA in this
example). At this point of time, SU S4 is standby for SIB and SIC also but SU1
is not quiesced for these two SIs. Due to this, SIB and SIC will be removed
from SU S4 and it will become active for SIA. Now SU S1 will be made standby
for all quiesced SIs (only one SIA in this example). Since standby assignments
from SIB and SIC are getting removed during the course of this operation, SU S1
will make standby for SIB and SIC by giving fresh assignments.
So in contrast to 2N redudancy model, flow of SI_SWAP operation in N+M
model can lead to removal of standby assignments and also fresh assignments.
**Notes on implementation: **
1)SI_SWAP operation will not be allowed if SI Equal distribution feature is
enabled in the SG.
2)Since SI dep within SU is not suported in N+M model, AMF will not honour SI
dep within SU while assigning Active or Quiesced HA state during the admin
operation.
3)Since Operation will lead to swap of all SIs assgined to the active SU,
operation will be rejected if anyone of these SIs does not have standby
assignments in some SU.
4) Operation will not be allowed if it will lead to violation of SG
configuration attrbiutes: saAmfSGMaxActiveSIsperSU, saAmfSGMaxStandbySIsperSU,
saAmfSGNumPrefActiveSUs and saAmfSGNumPrefStandbySUs.
**Changes in sg_npm_fsm.cc:** Some code related to switch operation is already
present. The same code will resued and enhanced for implementation. Most of the
code is under SI_OPER state of SG.
To be updated with more example configuration..
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