[EXTERNAL] Re: Managing heterogeneous systems

Neeraj Ladkani neladk at microsoft.com
Fri Jan 10 12:08:38 AEDT 2020

Thanks Richard for reviving this thread! 

Please count me in for the discussion. I will add few more points in your agenda discussion. 

1) Layer 2/3 discovery and negotiation
2) Caching, proxy, and consistency requirements
3) Target hardware, performance requirements, and scale of aggregation
4) Tooling and infrastructure improvements needed to support an aggregator
5) Amount of configuration and knowledge an aggregator needs to know a priori.
6) Data presentation from Inband?
7) Security  

I am also in PST and flexible on other time zones as well. 


From: Richard Hanley <rhanley at google.com> 
Sent: Thursday, January 9, 2020 2:21 PM
To: vishwa <vishwa at linux.vnet.ibm.com>
Cc: Neeraj Ladkani <neladk at microsoft.com>; 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: Re: [EXTERNAL] Re: Managing heterogeneous systems

I'm going to resurrect this thread for the new year.

It sounds like there is a decent need for some type of aggregator.  Would anyone be interested in setting up a meeting to try and synthesize our use cases into some broadly applicable requirements?

I'm located on the West Coast, but I have a pretty flexible schedule for other time zones next week.

Some topics for us to discuss (either in a meeting or offline) include:

1) Layer 2/3 discovery and negotiation
2) Caching, proxy, and consistency requirements
3) Target hardware, performance requirements, and scale of aggregation
4) Tooling and infrastructure improvements needed to support an aggregator
5) Amount of configuration and knowledge an aggregator needs to know a priori.

Any ideas on what else we can cover?  Is there a preferred format or medium that would work best to gather these higher level requirements?


On Thu, Dec 19, 2019 at 2:17 AM vishwa <mailto:vishwa at linux.vnet.ibm.com> wrote:
Thanks for putting it together.
On 12/13/19 1:32 AM, Richard Hanley wrote:
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 https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmembers.dmtf.org%2Fapps%2Forg%2Fworkgroup%2Fredfish%2Fdocument.php%3Fdocument_id%3D91811&data=02%7C01%7Cneladk%40microsoft.com%7C252332bdcf5a42f86b0408d795524ba2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637142053009953534&sdata=lFM7W0d%2FNFvUvIMJQYtfP3X3QCWN%2B2K0sv7bYbS5mFM%3D&reserved=0) 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.

Consider a hypothetical case where I have 4 compute nodes, each having BMC in it and that BMC is responsible for initiating power-on and other services for that node / getting the debug data out of that node / etc...
We would want an external Management Console(MC) to manage this rack. Instead of going to 4 nodes separately, MC can ask 1 BMC that I am calling as "Point Of Contact" BMC / Primary BMC for that rack. It is the job of that BMC to do whatever is needed to return the result.
Similarly, when the POC goes down, we would need another POC.
I believe, Redfish discovery can be used to discover each BMCs. But how does the heart beat work between discovered BMCs ?
Also, when the POC goes down, how can we sense that and make some other BMC as POC using Redfish framework ?

I have a control node that is housing 2 BMCs. One can be Primary and other can be Slave. Each BMC has the complete view of the whole systems. 
I am assuming, we could still discover the other BMC using Redfish.. But again, how do we exchange heartbeat and do failover operations ?
!! Vishwa !!
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.


On Wed, Dec 11, 2019 at 11:33 PM Neeraj Ladkani <mailto:neladk at microsoft.com> wrote:
Sure, how do we want to enable BMC-BMC communication? Standard redfish/IPMI ? 
From: vishwa <mailto:vishwa at linux.vnet.ibm.com> 
Sent: Wednesday, December 11, 2019 10:59 PM
To: Neeraj Ladkani <mailto:neladk at microsoft.com>
Cc: mailto:openbmc at lists.ozlabs.org; mailto:sgundura at in.ibm.com; mailto:kusripat at in.ibm.com; mailto:shahjsha at in.ibm.com; mailto:vikantan at in.ibm.com; Richard Hanley <mailto: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": {
        "@https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fodata.id&data=02%7C01%7Cneladk%40microsoft.com%7C252332bdcf5a42f86b0408d795524ba2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637142053009963532&sdata=xsL6Al0D3ddfNEBu4sI3MmXEHqNhTzaSLxsmvjffwXA%3D&reserved=0": "/redfish/v1/Systems"
    "Chassis": {
        "@https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fodata.id&data=02%7C01%7Cneladk%40microsoft.com%7C252332bdcf5a42f86b0408d795524ba2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637142053009963532&sdata=xsL6Al0D3ddfNEBu4sI3MmXEHqNhTzaSLxsmvjffwXA%3D&reserved=0": "/redfish/v1/Chassis"
    "Managers": {
        "@https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fodata.id&data=02%7C01%7Cneladk%40microsoft.com%7C252332bdcf5a42f86b0408d795524ba2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637142053009973528&sdata=nTXfOlL%2Ff0d5ALUa28%2BsrYSskTwYwihZ6yjCsaUsc%2Fk%3D&reserved=0": "/redfish/v1/Managers"
    "AccountService": {
        "@https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fodata.id&data=02%7C01%7Cneladk%40microsoft.com%7C252332bdcf5a42f86b0408d795524ba2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637142053009973528&sdata=nTXfOlL%2Ff0d5ALUa28%2BsrYSskTwYwihZ6yjCsaUsc%2Fk%3D&reserved=0": "/redfish/v1/AccountService"
    "SessionService": {
        "@https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fodata.id&data=02%7C01%7Cneladk%40microsoft.com%7C252332bdcf5a42f86b0408d795524ba2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637142053009983521&sdata=MuxyWv3I1qCNIfXIFHWTGPd66U6DXRqZNTzIViK1908%3D&reserved=0": "/redfish/v1/SessionService"
    "Links": {
        "Sessions": {
            "@https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fodata.id&data=02%7C01%7Cneladk%40microsoft.com%7C252332bdcf5a42f86b0408d795524ba2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637142053009983521&sdata=MuxyWv3I1qCNIfXIFHWTGPd66U6DXRqZNTzIViK1908%3D&reserved=0": "/redfish/v1/SessionService/Sessions"
3.  Custom Messaging over LAN ( PubSub)
I am also working on a whitepaper on same area ☺.  Happy to work with you guys if you have any ideas on how can we standardize this. 
From: vishwa mailto:vishwa at linux.vnet.ibm.com 
Sent: Tuesday, December 10, 2019 1:00 AM
To: Richard Hanley mailto:rhanley at google.com; Neeraj Ladkani mailto:neladk at microsoft.com
Cc: mailto:openbmc at lists.ozlabs.org; mailto:sgundura at in.ibm.com; mailto:kusripat at in.ibm.com; mailto:shahjsha at in.ibm.com; mailto: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?
*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 <mailto: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? 

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