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HPE Store Virtual CMC Map View and iSCSI connections

GBlyshchyk
Occasional Advisor

HPE Store Virtual CMC Map View and iSCSI connections

We have a Multi-site SAN consisting of three sites. In one site there is one storage (model 4330) and one server (ProLiant DL360p Gen8), in the second site one storage (model 4330) and two servers (ProLiant DL360p G7), in the third site we have FOM. These two storage units are in a cluster. A VIP is configured for the cluster.
The servers are connected to the storage system via an iSCSI connection. ProLiant DL360p G7 two connections through the Broadcom iSCSI Adapter, and the ProLiant DL360p Gen8 has two connections via the iSCSI Software Adapter.

If you look at the HPE StoreVirual CMC tab in the "Map View" tab, we'll see that all the servers are connected by active connections to only one storage. The other storage connections are inactive. The sessions tab shows that all servers are connected through one gateway connection. Sometimes, when systems are restarted (storage or servers) manually, all connections become active (we did not find a clear dependency).

The help is written "When using VIP and load balancing, one iSCSI session acts as the gateway session." All I / O goes through this iSCSI session. The Gateway Connection column displays the IP address of the storage system hosting the load balancing iSCSI session. "

But I want traffic from servers to remain within the site. Why does this happen or do I do not understand something and everything is normal?
There is one more thing: when connections are active only to one storage, then there may be delays in working with disks on servers. If the connections are active to all storage then there are no delays.

The servers are running esx 5.0. Path selection Round Robin

 

 

12 REPLIES
oikjn
Honored Contributor

Re: HPE Store Virtual CMC Map View and iSCSI connections

Just to confirm, have you assigned each node AND each initiator to a specific site in CMC?  That is required.  We use microsoft so I don't know the specific settings within esx, but what you sound like you aren't sure is working correctly is an MPIO connection.  When I connect iSCSI sessions using the HP DSM MPIO on my initiators, I see CMC reporting iSCSI sessions reporting as DSM paths.  Can you take a screen shot of some of your iscsi sessions for a LUN and post that here?

GBlyshchyk
Occasional Advisor

Re: HPE Store Virtual CMC Map View and iSCSI connections

Right. Each host initiator is in the same site, not in different.

GBlyshchyk
Occasional Advisor

Re: HPE Store Virtual CMC Map View and iSCSI connections

After the weekend, I saw that the picture has changed. All compounds became active. Why is this happening?

oikjn
Honored Contributor

Re: HPE Store Virtual CMC Map View and iSCSI connections

if all the initiators are assigned to one site and that is the same site as one of the TWO VSA nodes, then all the traffic will conect and flow through just the one node that is at the same site as the initiators.  This is by design AND it is exactly what you want to happen as it will minimize the bandwidth and latency associated with a multi-site cluster.  If the initiators are not assigned to any site or happen to be assigned to a 3rd or 4th site, then I'm not sure what will happen, but I'd guess they will talk to both nodes.   

GBlyshchyk
Occasional Advisor

Re: HPE Store Virtual CMC Map View and iSCSI connections

I just want to know why with such an assignment of sites, do you "Map View" active connections only show to one storage?
(I do not know how to add a few images to the server, so I specify a link to the post and attach the file)

screenshot 1 

oikjn
Honored Contributor

Re: HPE Store Virtual CMC Map View and iSCSI connections

that is the location.

from what I see, you have store4 and esx3-new at one site and store3 and esx1 and esx2 at another site.  Are these sites virtual or actually physically seporate?  If they are virtual, I would suggest that you move everything to a single site because there is no real benefit to such a setup unless you have many storage nodes and want to setup an additional fault domain isolation such as rack location.

From what you show there, the esx3-new server should only actively connect to the store4 node if the DSM MPIO is setup correctly and the esx1/2 servers should only connect to the store3 node.  This is by design with a multi-site setup because a multi-site setup assumes you have limited bandwidth and higher latency talking to a remote site, so all writes will happen to the local site first to minimize the transit and replication time/bandwidth.

GBlyshchyk
Occasional Advisor

Re: HPE Store Virtual CMC Map View and iSCSI connections

These sites are located in different geographically located places. Connected to each other through two optical lines that are united on the switches in a trunk (aggregate).
Each host (Vmware esxi) has two dedicated network cards for iSCSI traffic. Each network card bind to the VMkernel port.

oikjn
Honored Contributor

Re: HPE Store Virtual CMC Map View and iSCSI connections

So that does sound like a multi-site setup, but....  you might want to try converting it to a single site anyway.

I'm assuming that when you mention that fiber, that it is YOUR fiber and that you have the full 10G bandwidth of both links for your company use and that since its your company fiber it is likely a relitively short run (not 10's of km or more).  That implies that bandwidth and latency are no more of an issue than they would be across two racks located in the same server room.  Since you only have two nodes, the replication traffic and inefficienties of talking across that link are minor compared to something like a 4 or 6 node cluster.  

Since you only have two nodes, changing the site definitions for the nodes and the initiators to be just at one site will not cause a restripe of the LUNs as might happen when you have multiple nodes at each site.  Because of this, I would suggest you try converting the cluster to be a single site so that MPIO will talk to both nodes instead of just the local one.  If you find the latency or bandwidth is an issue, you can always convert it back to multi-site.  The conversion process is simply changing the site assignments in CMC.

GBlyshchyk
Occasional Advisor

Re: HPE Store Virtual CMC Map View and iSCSI connections

Thanks for trying to help. I will definitely try to make one site. But I would like to know, if possible, why on MapView are the active connections only to one store? Is this normal and I should not pay attention or is it a problem?

I mean why it does not work as written in the documentation - that if the host and storage are in the same site then the active connection should only be to it alone. I explain why I care about this - the documentation says that "All I / O passes through this iSCSI session when I use VIP and load balancing, one iSCSI session acts as the gateway session. , then clicking the iSCSI Sessions tab. The Gateway Connection column displays the IP address of the storage system hosting the load balancing iSCSI session. " If I correctly understood that in my case all traffic goes through one node. Or should the definitions of hosts and nodes in the sites influence the Gateway Connections?

oikjn
Honored Contributor

Re: HPE Store Virtual CMC Map View and iSCSI connections

you connect to the VIP address and then the DSM module will intelligently connect to the appropriate nodes according to CMC's site assignments.  Since you have one node at the site with the initiator that initiator will only actively connect to that one node unless that node fails and then it will fail over to the remote site node.

GBlyshchyk
Occasional Advisor

Re: HPE Store Virtual CMC Map View and iSCSI connections

I apologize, the language barrier seems to be affecting and I do not fully understand you. My main language is Russian and Belarusian.
You say "Since you have one node at the site with the initiator that initiator will only actively connect to that one node. I understand it this way: that the initiator connects to the node in one site.

But in fact it happens differently: each site has a node and a host with the initiator, all initiators of one host are in the same site. And I see that hosts (with initiators) from one site have an active connection to another site and do not have active connections to the site in which they themselves are located. This is normal? :)

oikjn
Honored Contributor

Re: HPE Store Virtual CMC Map View and iSCSI connections

what you just described is not normal and is the opposite of what it should be doing.  It sounds like somehow the sites are incorrectly defined for something.  

check out https://support.hpe.com/hpsc/doc/public/display?docId=c05049830 this should tell you how to setup MPIO to make sure it is configured correctly.  Either way, you shoudl still try converting the cluster to a single site in your specific situation (assuming I was correct that you do have 2x 10gb direct links with full bandwidth between the two sites which are located very close together).