[EXTERNAL] Re: Managing heterogeneous systems

[Richard Hanley]

In our case we are working to migrate away from IPMI to Redfish.  Most of
the solutions I've been thinking about have leaned pretty heavily into that.

In my mind I've sliced this project up into a few different areas.

*Merging/Transforming Redfish Resources*
Let's say that there are several Redfish services.  They will have
collections of Systems, Chassis, and Managers that need to be merged.  In
the simplest uses this would be just an HTTP proxy cache with some URL
cleaning.

However, this could end up being a pretty deep merge in cases where some
resources are split across multiple management domains.  Memory errors
being on one node, but the temperature sensor being on a separate node is a
good example. Another example would be the "ContainedBy" link.  These links
might reach across different BMC boundaries, and would need to be inserted
by the primary node.

*Aggregating Services and Actions*
This is where I think the DMTF proposals for Redfish aggregation (located
here
<https://members.dmtf.org/apps/org/workgroup/redfish/document.php?document_id=91811>)
provide the most insight.  My reading of this proposal is that an
aggregation service would be used to tie actions together.  For example,
there may be individual chassis reset action embedded in the chassis
resources, and then aggregated action for a full reset.

DMTF seems to be leaving the arbiter of the aggregation up to the
implementation.  I'd imagine that some implementations would provide a
static aggregation service, while others would allow clients to create
their own dynamic aggregates.

*Discovery, Negotiation, and Error Recovery*
This is an area where I'd like to hear more about your requirements,
Vishwa.  Would you expect the BMC cluster to be hot-swappable?  Is there a
particular reason that it has to be peer to peer? What kind of error
recovery should be supported when a node fails?

At a high level, the idea that has been suggested internally is to have a
designated master node at install time.  That node would discover any other
Redfish services on the LAN, and begin aggregating them.  The master node
would keep any in memory cache of the other services, and reload resources
on demand.  If a node goes down, then there error is propagated using HTTP
return codes.  If the master node goes down, then the entire aggregate will
go down.  In theory a client could talk to individual nodes if it needed to.

* Authentication and Authorization*
This is an area where I think Redfish is a little hands off.  In an ideal
world ACLs could be setup without proliferating username/passwords across
nodes.  As an aside, we've been thinking about how to use Redfish without
any usernames or passwords.  By using a combination of certificates and
authorization tokens it should be possible to extend a security zone to a
small cluster of BMCs.

Regards,
Richard

On Wed, Dec 11, 2019 at 11:33 PM Neeraj Ladkani <neladk at microsoft.com>
wrote:

> Sure, how do we want to enable BMC-BMC communication? Standard
> redfish/IPMI ?
>
>
>
> Neeraj
>
>
>
>
>
> *From:* vishwa <vishwa at linux.vnet.ibm.com>
> *Sent:* Wednesday, December 11, 2019 10:59 PM
> *To:* Neeraj Ladkani <neladk at microsoft.com>
> *Cc:* openbmc at lists.ozlabs.org; sgundura at in.ibm.com; kusripat at in.ibm.com;
> shahjsha at in.ibm.com; vikantan at in.ibm.com; Richard Hanley <
> rhanley at google.com>
> *Subject:* Re: [EXTERNAL] Re: Managing heterogeneous systems
>
>
>
> On 12/10/19 3:20 PM, Neeraj Ladkani wrote:
>
> Great discussion.
>
>
>
> The problem is not physical interface as they can communicate using LAN.
> The problem is entity binding as one compute node can be connected to 1 or
> more storage nodes. How can we have one view of system from operational
> perspective? Power on/off, SEL logs, telemetry?
>
>
>
>
> Correct. This is where I mentioned about "Primary BMC acting as Point Of
> Contact" for external requests.
> Depending on how we want to service the request, we could orchestrate that
> via PoC BMC or respond to external requesters on where they can get the
> data and they connect to 'em directly.
>
>
> !! Vishwa !!
>
>
>
> Some of problems :
>
>
>
>    1. Power operations : Power/resets/ need to be coordinated in all
>    nodes in a system
>    2. Telemetry : OS runs only on head node so if there are requests to
>    read telemetry, it should get telemetry ( SEL logs, Sensor Values ) from
>    all the nodes.
>    3. Firmware Update
>    4. RAS: Memory errors are logged by UEFI SMM in to head node but
>    corresponding DIMM temperature , inlet temperature are logged on secondary
>    node which are not mapped.
>
>
>
>
>
> I have been exploring couple of routes
>
>
>
>    1. LUN  discovery and routing: this is similar to IPMI but I am
>    working on architecture to extend this to support multiple LUNs and route
>    them from Head node. ( we would need LUN routing over LAN )
>    2. Redfish hierarchy for systems
>
>    "Systems": {
>
>         "@odata.id": "/redfish/v1/Systems"
>
>     },
>
>     "Chassis": {
>
>         "@odata.id": "/redfish/v1/Chassis"
>
>     },
>
>     "Managers": {
>
>         "@odata.id": "/redfish/v1/Managers"
>
>     },
>
>     "AccountService": {
>
>         "@odata.id": "/redfish/v1/AccountService"
>
>     },
>
>     "SessionService": {
>
>         "@odata.id": "/redfish/v1/SessionService"
>
>     },
>
>     "Links": {
>
>         "Sessions": {
>
>             "@odata.id": "/redfish/v1/SessionService/Sessions"
>
>         }
>
> 3.  Custom Messaging over LAN ( PubSub)
>
>
>
> I am also working on a whitepaper on same area J.  Happy to work with you
> guys if you have any ideas on how can we standardize this.
>
>
>
> Neeraj
>
>
>
> *From:* vishwa <vishwa at linux.vnet.ibm.com> <vishwa at linux.vnet.ibm.com>
> *Sent:* Tuesday, December 10, 2019 1:00 AM
> *To:* Richard Hanley <rhanley at google.com> <rhanley at google.com>; Neeraj
> Ladkani <neladk at microsoft.com> <neladk at microsoft.com>
> *Cc:* openbmc at lists.ozlabs.org; sgundura at in.ibm.com; kusripat at in.ibm.com;
> shahjsha at in.ibm.com; vikantan at in.ibm.com
> *Subject:* [EXTERNAL] Re: Managing heterogeneous systems
>
>
>
> Hi Richard / Neeraj,
>
> Thanks for bringing this up. It's one of the interesting topic for IBM.
>
> Some of the thoughts here.....
>
> When we have multiple BMCs as part of a single system, then there are 3
> main parts into it.
>
> 1/. Discovering the peer BMCs and role assignment
> 2/. Monitoring the existence of peer BMCs - heartbeat
> 3/. In the event of loosing the master, detect so using #2 and then
> reassign the role
>
> Depending on how we want to establish the roles, we could have
> Single-Master, Many-slave or Multi-Master, Multi-Slave. etc
>
> One of the team here is trying to do a POC for Multi BMC architecture and
> is still in the very beginning stage.
> The team is currently studying/evaluating the available solution -
> Corosync / Heartbeat / Pacemaker".
> Corosync works nice with the clusters, but we need to see if we can trim
> it down for BMC.
>
> If we can not use corosync for some reason, then need to see if we can use
> the discovery using PLDM ( probably use the terminus IDs )
> and come up with custom rules for assigning Master-Slave roles.
>
> If we choose to have Single-Master and Many-Slave, we could have that
> Single-Master as an entity acting as a Point of Contact for external
> request and then could orchestrate with the needed BMCs internally to get
> the job done
>
> I will be happy to know if there are alternatives that suit BMC kind of an
> architecture
>
> !! Vishwa !!
>
> On 12/10/19 4:32 AM, Richard Hanley wrote:
>
> Hi Neeraj,
>
>
>
> This is an open question that I've been looking into as well.
>
>
>
> For BMC to BMC communication there are a few options.
>
>    1. If you have network connectivity you can communicate using Redfish.
>    2. If you only have a PCIe connection, you'll have to use either the
>    inband connection or the side band I2C*.  PLDM and MCTP are protocols that
>    defined to handle this use case, although I'm not sure if the OpenBMC
>    implementations have been used in production.
>    3. There is always IPMI, which has its own pros/cons.
>
> For taking several BMCs and aggregating them into a single logical
> interface that is exposed to the outside world, there are a few things
> happening on that front.  DMTF has been working on an aggregation protocol
> for Redfish.  However, it's my understanding that their proposal is more
> directed at the client level, as opposed to within a single "system".
>
>
>
> I just recently joined the community, but I've been thinking about how a
> proxy layer could merge two Redfish services together.  Since Redfish is
> fairly strongly typed and has a well defined mechanism for OEM extensions,
> this should be pretty generally applicable.  I am planning on having a
> white paper on the issue sometime after the holidays.
>
>
>
> Another thing to note, recently DMTF released a spec for running a binary
> Redfish over PLDM called RDE.  That might be a useful way of tying all
> these concepts together.
>
>
>
> I'd be curious about your thoughts and use cases here.  Would either PLDM
> or Redfish fit your use case?
>
>
>
> Regards,
>
> Richard
>
>
>
> *I've heard of some proposals that run a network interface over PCIe.  I
> don't know enough about PCIe to know if this is a good idea.
>
>
>
> On Mon, Dec 9, 2019 at 1:27 PM Neeraj Ladkani <neladk at microsoft.com>
> wrote:
>
> Are there any standards in managing heterogeneous systems? For example in
> a rack if there is a compute node( with its own BMC) and storage node( with
> its own BMC) connected using a PCIe switch.  How these two BMC represented
> as one system ?  are there any standards for BMC – BMC communication?
>
>
>
>
>
> Neeraj
>
>
>
>
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