EMC VPLEX : Extending VMWare Functionality Across Data Centers

VPLEX is a storage virtualization appliance. It sits between the storage arrays and hosts and virtualizes the presentation of storage arrays, including non-EMC arrays. Storage is then configured and presented to the host. It delivers data mobility and availability across arrays and sites. VPLEX is a unique virtual storage technology that enables mission critical applications to remain up and running during any of a variety of planned and unplanned downtime scenarios. VPLEX permits painless, nondisruptive data movement, taking technologies like VMware and other clusters that were built assuming a single storage instance and enabling them to function across arrays and across distance. 

VPLEX key use cases comprise:

• Continuous operations – VPLEX enables active/active data centers with zero downtime
• Migration/tech refresh – VPLEX provides accelerated and nondisruptive migrations and technology refresh
• Oracle RAC functionality – VPLEX extends Oracle Real Application Clusters (RAC) and other clusters over distance
• VMware functionality – VPLEX extends VMware functionality across distance while enhancing availability
• MetroPoint Topology – VPLEX with EMC RecoverPoint delivers a 3-site continuous protection and operational recovery solution

The EMC VPLEX family includes three models:

EMC VPLEX Local:

EMC VPLEX Local delivers availability and data mobility across arrays. VPLEX is a continuous availability and data mobility platform that enables mission-critical applications to remain up and running during a variety of planned and unplanned downtime scenarios.

EMC VPLEX Metro:

EMC VPLEX Metro delivers availability and data mobility across sites. VPLEX Metro with AccessAnywhere enables active-active, block level access to data between two sites within synchronous distances.  Host application stability needs to be considered. It is recommended that depending on the application that consideration for Metro be =< 5ms latency. The combination of virtual storage with VPLEX Metro and virtual servers allows for the transparent movement of VM’s and storage across longer distances and improves utilization across heterogeneous arrays and multiple sites.

EMC VPLEX Geo:

EMC VPLEX Metro delivers availability and data mobility across sites. VPLEX Geo with AccessAnywhere enables active-active, block level access to data between two sites within asynchronous distances. Geo improves the cost efficiency of resources and power.  It provides the same distributed device flexibility as Metro but extends the distance up to 50ms of network latency. 

NX-OS Overview

The cisco NX-OS , next generation operating system was built with modularity, resiliency and serviceability at its foundation. It is based on SAN-OS(Cisco Storage Area Network-Operating System).

Advantage of NX-OS:

1. Unified data center operating system: NX-OS can handle both LAN traffic and SAN traffic.

2. Robust and rich feature set with a variety of Cisco Innovations: Features like ISSU and             PSS(described later)

3. Flexibility and scalability :

4. Modularity : Virtual Device Contexts (VDC)

5. Virtualization :

6. Resiliency

7. IPv4 and IPv6 ip routing and multicast features

8.Comprehensive security , availability, serviceability and management features

Key Features and benefits of NX-OS

1.  Virtual Device Contexts: Available on Cisco Nexus 7000 switches only, these switches can be segmented into multiple virtual devices. These virtual devices function as independent switches and can run independent of each other. VDCs provide benefits like fault isolation, administration plane, seperation of data traffic and enhanced security.

2. Virtual Port Channels(VPCs) : This feature enables a server or switch to use an EtherChannel across two upstream switches without and STP blocked port to enable use of all available uplink bandwidth.

3. Continuous System Operation : Maintenance , upgrades and software certifications can be performed without service interruptions because of the modular nature of NX-OS and features such as In Service Software Upgrade and the ability for processes to restart dynamically.

4. Security : Cisco NX-OS provides outstanding data confidentiality and integrity, supporting standard IEEE 802.1AE link-layer cryptography with 128-bit Advanced Encryption Standard (AES) cryptography. In addition to CTS, there are many additional security features such as access control lists (ACLs) and port-security.

5. Overlay Transport Virtualization (OVT) : Enables layer 2 extension between distributed data centers over any transport layer 3 network.

6. NX-OS Persistant Storage Service :  The PSS is a lightweight database that maintains runtime information state. PSS provides reliable persistant storage to the software components to checkpoint their internal state and data structures enabling non-disruptive restart . If a fault occurs in a process such as OSPF the NX-OS high availability (HA) manager determines best recovery action.

• Restart a process
• Switch over to a redundant supervisor module

7. Fabric Path : This is similar to link state protocol which enables each device to build an overall view of the topology. Each device is identified by a swtich id. This eliminates spanning tree to maximize network bandwidth and flexibility.

For more datails on fabric path refer to : Fabric Path

Introduction to Fabric Path

What is Fabric Path ?

        Cisco Fabric Path is an innovation in Cisco NX-OS software that brings the stability and performance of Layer 3 routing to Layer 2 switched networks to build a highly resilient and scalable Layer 2 fabric. Cisco FabricPath is a foundation for building massively scalable and flexible data centers.. Thus it is a layer 2 routing protocol also sometimes called MAC in MAC Routing.

This is an alternative to running STP. Thus if there is a layer 2 failure due to link cut or layer 2 crash, the entire spanning tree does not need to re-converge which is a feature of STP thus increasing the availabilty of the system. In addition to that, there are no redundant paths as in STP which gives higher bandwidth between the switches by implementing equal cost paths among the links.

How does it work ?

        Cisco Fabric  Path introduces entirely new Layer 2 data plane by encapsulating the frames entering the fabric with a header that consists of routable source and destination addresses. These addresses are called Switch IDs. These addresses are the address of switch in which the frame was received and the address of the destination switch to which the frame is heading. From there the frame is routed until it reaches the remote switch where it is decapsulated and delivered in its original Ethernet format. The figure below shows this simple process.

Fabric Path Terminologies:

Classical Ethernet (CE): It is the regular ethernet with regular flooding and regular STP etc.

The classical ethernet domain has been marked with green border in the figure above.

Leaf Switches : These switches connect CE(Classical Ethernet) domain to FP(Fabric Path) domain.

The switches in the middle of the picture are the leaf switches which are implemented using nexus 5k devices, more precisely nexus 5500 and 7000 F1 and F2 line card modules as nexus 5000 does not support fabric path because fabric path is implemented in hardware.

Spine Swtiches: These switches FP backbone switch with all ports in the FP domain only. The switches on the top of the picture are the spine switches which are implemented using nexus 7k devices.

FP Core Ports: Links the leaf up to spine or between spine switches. The ports in nexus switches are by default in classical ethernet mode ie access mode. Ports within the red border in above picture.To configure it for fabric path the following command should be used.

N7K-1#conf t

N7K-1(config)#int ethernet 1/1

N7K-1(config-if)#switchport mode fabricpath

CE Edge Ports: These ports link the leaf switches connecting to regular classical ethernet domain.

Ports within the green border in above picture.

Fabric Path Switch ID:

           This is analogous to OSPF router id or IS-IS NET id. This identifies the node in IS-IS SPT(Shortest path tree).  This id is automatically generated by default. It can also be assigned manually using the following command in global config mode.

N7K-1#conf t

N7K-1(config)#fabricpath switch-id

Fabric Path Control Plane:

FabricPath IS-IS replaces STP as the control-plane protocol within the FabricPath domain. In other words, FabricPath IS-IS determines the forwarding topology STP(Shortest path tree) instead of STP(Spanning Tree Protocol).    

IS-IS is an industry standard link-state routing protocol. The FabricPath IS-IS implementation is implemented as a single-level IS-IS domain and extended through the definition of FabricPath-specific Type-Length-Value (TLV) fields.

Several characteristics of IS-IS make it ideally suited for use as a Layer 2 forwarding protocol:

●   Has no IP dependency - IS-IS does not require IP reachability in order to form adjacency between devices. While the majority of modern networks do provide IP connectivity for network infrastructure, using IS-IS ensures that no strict requirement for in-band IP connectivity among switches exists.It does not use IP to carry routing information messages. IS-IS is neutral regarding the type of network addresses for which it can route.

●   Easily extensible - Using custom TLVs, IS-IS devices can exchange information about virtually anything. In the case of Layer 3 IS-IS, routers exchange IP prefix reachability. In the case of FabricPath, switches exchange Switch ID reachability.

●   Provides SPF routing - SPF routing protocols have been proven to be scalable, flexible, and fast to converge. In addition, IS-IS supports equal-cost multipath (ECMP) forwarding, allowing data-plane packets to follow any available parallel path rather than restricting forwarding to a single path.

While IS-IS forms the basis of FabricPath, enabling FabricPath in your network requires no specific knowledge of IS-IS - the configuration is plug-and-play. Much as a network operator simply “turns on” STP and interconnects switches, you can enable FabricPath on interfaces and begin forwarding through the FabricPath fabric with minimal configuration.