Force10 and vSphere vDS Interoperability Issue

Recently I had an opportunity to work with Dell FX2 platform from the design and delivery point of view. I was deploying a FX2s chassis with FC630 blades and FN410S 10Gb I/O aggregators.

I ran into an interesting interoperability glitch between Force10 and vSphere distributed switch when using LLDP. LLDP is an equivalent of Cisco CDP, but is an open standard. And it allows vSphere administrators to determine which physical switch port a given vSphere distributed switch uplink is connected to. If you enable both Listen and Advertise modes, network administrators can get similar visibility, but from the physical switch side.

In my scenario, when LLDP was enabled on a vSphere distributed switch, uplinks on all ESXi hosts started disconnecting and connecting back intermittently, with log errors similar to this:

Lost uplink redundancy on DVPorts: “1549/03 4b 0b 50 22 3f d7 8f-28 3c ff dd a4 76 26 15”, “1549/03 4b 0b 50 22 3f d7 8f-28 3c ff dd a4 76 26 15”, “1549/03 4b 0b 50 22 3f d7 8f-28 3c ff dd a4 76 26 15”, “1549/03 4b 0b 50 22 3f d7 8f-28 3c ff dd a4 76 26 15”. Physical NIC vmnic1 is down.

Network connectivity restored on DVPorts: “1549/03 4b 0b 50 22 3f d7 8f-28 3c ff dd a4 76 26 15”, “1549/03 4b 0b 50 22 3f d7 8f-28 3c ff dd a4 76 26 15”. Physical NIC vmnic1 is up

Uplink redundancy restored on DVPorts: “1549/03 4b 0b 50 22 3f d7 8f-28 3c ff dd a4 76 26 15”, “1549/03 4b 0b 50 22 3f d7 8f-28 3c ff dd a4 76 26 15”, “1549/03 4b 0b 50 22 3f d7 8f-28 3c ff dd a4 76 26 15”, “1549/03 4b 0b 50 22 3f d7 8f-28 3c ff dd a4 76 26 15”. Physical NIC vmnic1 is up

Issue Troubleshooting

FX2 I/O aggregator logs were reviewed for potential errors and the following log entries were found:

%STKUNIT0-M:CP %DIFFSERV-5-DSM_DCBX_PFC_PARAMETERS_MISMATCH: PFC Parameters MISMATCH on interface: Te 0/2

%STKUNIT0-M:CP %IFMGR-5-OSTATE_DN: Changed interface state to down: Te 0/2

%STKUNIT0-M:CP %IFMGR-5-OSTATE_UP: Changed interface state to up: Te 0/2

This clearly looks like some DCB negotiation issue between Force10 and the vSphere distributed switch.

Root Cause

Priority Flow Control (PFC) is one of the protocols from the Data Center Bridging (DCB) family. DCB was purposely built for converged network environments where you use 10Gb links for both Ethernet and FC traffic in the form of FCoE. In such scenario, PFC can pause Ethernet frames when FC is not having enough bandwidth and that way prioritise the latency sensitive storage traffic.

In my case NIC ports on Qlogic 57840 adaptors were used for 10Gb Ethernet and iSCSI and not FCoE (which is very uncommon unless you’re using Cisco UCS blade chassis). So the question is, why Force10 switches were trying to negotiate FCoE? And what did it have to do with enabling LLDP on the vDS?

The answer is simple. LLDP not only advertises the port numbers, but also the port capabilities. Data Center Bridging Exchange Protocol (DCBX) uses LLDP when conveying capabilities and configuration of FCoE features between neighbours. This is why enabling LLDP on the vDS triggered this. When Force10 switches determined that vDS uplinks were CNA adaptors (which was in fact true, I was just not using FCoE) it started to negotiate FCoE using DCBX. Which didn’t really go well.

Solution

The easiest solution to this problem is to disable DCB on the Force10 switches using the following command:

# conf t
# no dcb enable

Alternatively you can try and disable FCoE from the ESXi end by using the following commands from the host CLI:

# esxcli fcoe nic list
# esxcli fcoe nic disable -n vmnic0

Once FCoE has been disabled on all NICs, run the following command and you should get an empty list:

# esxcli fcoe adapter list

Conclusion

It is still not clear why PFC mismatch would cause vDS uplinks to start flapping. If switch cannot establish a FCoE connection it should just ignore it. Doesn’t seem to be the case on Force10. So if you run into a similar issue, simply disable DCB on the switches and it should fix it.

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RecoverPoint VE: iSCSI Network Design

RecoverPoint is a great storage replication product, which supports Continuous Data Protection (CDP) and gives you RPO figures measured in second compared to a standard asynchronous storage-based replication solutions, where RPO is measured in minutes or even hours.

RecoverPoint comes in three flavours:

• RecoverPoint SE/EX/CL – physical appliance for replication between VNX (RecoverPoint/SE), VNX/VMAX/VPLEX (RecoverPoint/EX) or EMC and non-EMC (RecoverPoint CL) storage arrays.
• RecoverPoint VE – virtual edition of RecoverPoint which is installed as a VM and supports the same SE/EX/CL versions.
• RecoverPoint for Virtual Machines – also a virtual appliance but is array-agnostic and works at a hypervisor level by replicating VMs instead of LUNs.

In this blog post we will be discussing connectivity options for RecoverPoint VE (SE edition). Make sure to not confuse RecoverPoint VE and RecoverPoint for Virtual Machines as it’s two completely different products.

VNX MirrorView ports

MirrorView is an another EMC replication solution integrated into VNX arrays. If there’s a MirrorView enabler installed, it will claim itself the first FC port and the first iSCSI port. When patching VNX iSCSI ports make sure to NOT use the ports claimed by MirrorView.

If you use 1GbE (4-port) I/O modules you can use three ports per SP (all except port 0) and if you have 10GbE (2-port) I/O modules you can use one port per SP. I will talk about workarounds for this in the next blog post.

RPA appliance iSCSI vNICs

Each RecoverPoint appliance has two iSCSI NICs, which can be configured on either one or two subnets. If you use one 10Gb port on each SP as in the example above, then you’re forced to use one subnet. Because you obviously need at least two ports on each SP to have two networks.

If you have 1Gb modules in your VNX array, then you will most likely have two 1Gb iSCSI ports connected on each SP. In that case you can use two iSCSI subnets to reduce the number of iSCSI sessions between RPAs and a VNX.

On the vSphere side you will need to create one or two iSCSI port groups, depending on how many subnets you’ve decided to allocate and connect RPA vNICs accordingly.

VNX iSCSI Connections

RecoverPoint clusters are deployed and connected using a special tool called Deployment Manager. It assigns all IP addresses, connects RecoverPoint clusters to VNX arrays and joins sites together.

Once deployment is finished you will have iSCSI connections created on the VNX array. Depending on how many iSCSI subnets you’re using, iSCSI connections will be configured accordingly.

1. One Subnet Example

Lets look at the one subnet topology first. In this example you have one 10Gb port per VNX SP and two ports on each of the two RPAs all on one subnet. When you right click on the storage array in Unisphere and select iSCSI > Connections Between Storage Systems you should see something similar to this.

As you can see ports iSCSI1 and iSCSI2 on RPA0 and RPA1 are mapped to two ports on the storage array A-5 and B-5. Four RPA ports are connected to two VNX ports which gives you eight iSCSI initiator records on the VNX.

2. Two Subnets Example

If you connect two 1Gb ports per VNX SP and decide to use two subnets, then each SP will have one port on each of the two subnets. Same goes for the RPAs. Each RPA will have one vNIC connected to each subnet.

iSCSI connections will be set up a little bit differently now. Because only the VNX and RPA ports which are on the same subnet should be able to talk to each other.

Every RPA in this example has one IP on the xxx.xxx.46.0/255.255.255.192 subnet (iSCSI A) and one IP on the xxx.xxx.46.64/255.255.255.192 subnet (iSCSI B). Similarly, ports A-10 and B-10 on the VNX are configured on iSCSI A subnet. And ports A-11 and B-11 are configured on iSCSI B subnet. Because of that, iSCSI1 ports are mapped to ports A-10/B-10 and iSCSI2 ports are mapped to ports A-11/B-11.

As we are using two subnets in this example instead of 4 RPA ports by 4 VNX ports = 16 iSCSI connections, we will have 2 RPA ports by 2 VNX ports (subnet iSCSI A) + 2 RPA ports by 2 VNX ports (subnet iSCSI B) = 8 iSCSI connections.

Conclusion

The goal of this post was to discuss the points which are not very well explained in RecoverPoint documentation. It’s not a comprehensive guide by any means. You can find the full deployment procedure with prerequisites, installation and configuration steps in EMC RecoverPoint Installation and Deployment Guide.