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Implementing vSphere Metro Storage Cluster using Hitachi Storage Cluster for VMware vSphere (featuring Hitachi Virtual Storage Platform) (2039406)

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Purpose

This article provides information about deploying a metro storage cluster across two datacenters using Hitachi Virtual Storage Platform (VSP). With vSphere 5.0, a storage virtualization device can be supported in a metro storage cluster configuration.

Resolution

What is vSphere Metro Storage Cluster?

vSphere Metro Storage Cluster is a new storage configuration for VMware vSphere environments. A product must be certified via the VMware vMSC certification process, after which it is recognized with a unique hardware compatibility list category. All supported storage devices are listed in the VMware Storage Compatibility Guide.

What is Hitachi Virtual Storage Platform?

Hitachi Virtual Storage Platform (VSP) is the first 3-D scaling storage platform designed for all data types. Its storage architecture flexibly adapts for performance, capacity, and multivendor storage.
  • Scale Up — Meet increasing demands by dynamically adding processors, connectivity, and capacity in a single unit. Provide the highest performance for both open and mainframe environments.
  • Scale Out — Meet multiple demands by dynamically combining multiple units into a single logical system with shared resources. Support increased demand in virtualized server environments. Ensure safe multitenancy and quality of service through partitioning of cache and ports.
  • Scale Deep — Extend storage value by virtualizing new and existing external storage systems dynamically. Extend the advanced functions of Hitachi Virtual Storage Platform to multivendor storage. Offload less-demanding data to external tiers to save costs and to optimize the availability of tier-1 resources.

Two VSP storage systems can be configured in a stretched metro cluster configuration by leveraging built-in features such as Hitachi High Availability Manager and Hitachi TrueCopy® Remote Replication. This stretched configuration can provide service to 2 datacenters located within 300 kilometers of one another. Data volumes, including VMFS datastores, in this stretched configuration are highly available, and can be accessed by vSphere hosts on both sites simultaneously. In case of a site failure, the remaining data center VSP storage system continues to provide I/O access to the data volumes.

What are Hitachi High Availability Manager and the Hitachi Availability Manager Quorum Disk?

Built on the way VSP manages virtualized devices, Hitachi High Availability Manager administers internal storage and externally attached heterogeneous storage with common and integrated management. It is used in conjunction with Hitachi TrueCopy storage system-based replication technology, which synchronizes data between the designated primary copy, or P-VOL, and the remote secondary copy, or S-VOL.

Hitachi Dynamic Link Manager is multipathing software that integrates with Hitachi High Availability Manager (HAM) to provide load balancing and path failover capabilities for vSphere hosts (HDLM SATP and HDLM PSP). HDLM will load-balance I/O between all available paths from P-VOL and keep all paths to S-VOL as standby paths.

A 47MB LUN is created on an external storage array such as Hitachi Unified Storage 150 or other existing arrays, including Hitachi Adaptable Modular Storage 2000 or supported 3rd-party storage for use as a quorum disk. This LUN is presented to the Site 1 VSP and Site 2 VSP as externalized storage by virtue of VSP storage virtualization device capability. The quorum disk stores continually updated information about data consistency in Hitachi High Availability Manager for use during site failover operations. High Availability Manager uses the information in the event of a failure, to direct host operations to the secondary volume.
 
 

Configuration Requirements

These requirements must be satisfied to support this configuration:

  • The round-trip latency between the Ethernet networks in the two sites must be less than 10 milliseconds (uniform host access). The IP network supports the VMware ESXi hosts and the VSP/HAM management interface.
  • The round-trip latency for synchronous storage replication must be less than 5 milliseconds .
  • The minimum throughput available between the two sites should be 622 Mbps, in order to support vMotion of virtual machines across ESXi hosts spread across both data centers.
  • The ESXi hosts in both data centers must have a private network on the same IP subnet and broadcast domain.
  • VMware vCenter Server must be accessible from all vSphere hosts on both sites.
  • The same IP network on which the virtual machines reside must be accessible to ESXi hosts on both sites, so that clients accessing virtual machines running on ESXi hosts on both sites are able to function smoothly upon any VMware HA-triggered virtual machine restart event.
  • The data storage locations, including the boot device used by the virtual machines, must be accessible from ESXi hosts in both data centers.
  • The maximum number of vSphere hosts in the HA cluster must not exceed 32.
  • Hitachi Dynamic Link Manager v7.2 or newer is required.
  • Hitachi Virtual Storage Platform microcode v70.02 or newer is required.

Notes:

  • The Hitachi Storage Cluster solution only supports uniform host access, meaning that the vSphere hosts at each site can access the VSP P-VOLs provisioned from the opposite site.

For any additional requirements for Hitachi Storage Cluster, see the Deploy VMware vSphere Metro Storage Cluster on Hitachi Virtual Storage Platform reference architecture document.

Solution Overview

A VMware vSphere Metro Storage Cluster architecture on Hitachi Virtual Storage Platform provides an ideal solution for maximizing availability and uptime by clustering physical data centers within metro distances. The metro storage cluster solution from Hitachi Data Systems consists of storage systems presenting replicated storage as a single LUN from different geographically distributed sites. This design enables high availability of services by allowing virtual machine migration between sites with no downtime.

A combination of Hitachi software and hardware provides the following key functions to a vSphere infrastructure:

  • Host multipathing
  • Internal and external storage provisioning
  • Synchronous storage replication across metro cluster distances
  • Storage failover
These functions work together with VMware vSphere vMotion, vSphere High Availability, and vSphere Distributed Resource Scheduler to build this solution for a VMware vSphere Metro Storage Cluster. The advanced functionalities found in Virtual Storage Platform fulfill the requirements of a virtual infrastructure and reduce the need for additional hardware that may be required in traditional metro storage cluster solutions.

This solution uses a uniform host access configuration. In a uniform host access configuration, a primary datastore is synchronously replicated to a read-only secondary datastore. ESXi hosts from different sites can access the storage devices on both sites, but see the two LUNs as a single datastore.

These components create a VMware vSphere Metro Storage Cluster environment:
  • vSphere 5.0 ESXi hosts — The physical hosts on both data centers running the virtual machines and managed by vCenter Server
  • Hitachi Virtual Storage Platform — High-performance and highly scalable storage solution
  • Hitachi Unified Storage or existing Hitachi Adaptable Modular Storage or other supported 3rd-party storage systems — Midrange storage platform that provides reliable, flexible, scalable, and cost-effective modular storage, used by Hitachi High Availability Manager Quorum Disk
  • Hitachi Dynamic Link Manager — Multipathing software that integrates with Hitachi High Availability Manager to provide load balancing and path failover capabilities for servers
  • Hitachi TrueCopy® Remote Replication — Synchronous storage replication between storage systems
  • Hitachi High Availability Manager — Storage failover coordination; allows hosts to see a pair of replicated LUNs as a single datastore
  • Fibre Channel switch — SAN connectivity to the datacenter storage network
  • Network switch — LAN connectivity to the datacenter network
This image shows an overview of the VMware vSphere environment that has been tested for vMSC Certification:
 
 
This table lists the software components handling the management for host path failover and storage replication control: 
 
Metro Cluster software components Version
Hitachi Dynamic Link Manager 7.2.0-00 or newer
VMware vSphere command-line interface 5.0
Command control interface for Hitachi products 01-25-03/11 or newer
 

Tested Scenarios

This table outlines the tested and supported failure scenarios when using a Hitachi Storage Cluster for VMware vSphere with Hitachi Virtual Storage Platform:
 
Scenario
HAM/HDLM Behavior
Observed VMware behavior
Using VMware vMotion or VMware Distributed Resource Scheduler to migrate virtual machines between site 1 and site 2
No impact
Virtual machine migrates to site 2 hosts and I/O is directed to P-VOL on site 1. Hosts within the cluster will use active paths to P-VOL
Using VMware High Availability to failover virtual machines between site 1 and site 2
No impact
Virtual machine fails over to site 2 hosts and I/O is directed to P-VOL on site 1
An active path to the P-VOL fails
Host I/O is redirected to an available active path via HDLM PSP
  • Another active path is used
  • No disruption to virtual machines
Main Control Unit (MCU) system fails or all active paths to the MCU system hosting the P-VOL fail
Storage failover
  • Hitachi High Availability Manager verifies data integrity with the quorum disk before failover
  • High Availability Manager splits pair replication and S-VOL is converted to a write enabled status
  • Host I/O is redirected via HDLM SATP to the S-VOL
  • Active paths to P-VOL are reported dead
  • Standby paths to S-VOL become active
  • No disruption to virtual machines
All active paths to the P-VOL Fail for any ESXi host in the cluster.
  • Same behavior as Storage failover
  • When one host loses access to the P-VOL, all hosts in the cluster fail to the S-VOL to avoid a split-brain scenario
  • Active paths to P-VOL are reported dead
  • Standby paths to S-VOL become active
  • No disruption to virtual machines
Quorum disk fails or all paths to quorum disk removed
  • Replication between P-VOL and S-VOL stop with P-VOL suspending replication due to error condition (PSUE) and S-VOL in a suspended read-only state (SSUS)
  • Failover does not occur
  • I/O continues to active P-VOL paths
No impact
Storage replication link failure
  • Replication between P-VOL and S-VOL stop with P-VOL suspending replication due to error condition (PSUE) and S-VOL in a suspended read-only state (SSUS)
  • Failover does not occur
  • I/O continues to active P-VOL paths
No impact
WAN storage link failure
  • P-VOL cannot process host I/O from site 2; storage failover occurs
  • Site 1: After storage failover, S-VOL cannot process host I/O from site 1 hosts since Fibre Channel connections across sites are down
  • Site 1: Virtual machines on site 1 hosts are unable to access their virtual disks on site 2. Site 1 hosts must be shut down manually for VMware High Availability to restart virtual machines on site 2 hosts.
  • Site 2: After storage failover, S-VOL process host I/O for site 2 hosts because local site access remains active. Virtual machines on site 2 can access the local S-VOL
Primary Site failure
  • High Availability Manager verifies data integrity with the quorum disk before failover
  • High Availability Manager splits pair replication and S-VOL is converted to a write- enabled status (SSWS)
  • Host I/O is redirected via Hitachi Dynamic Link Manager SATP to the S-VOL
  • VMware High Availability fails over virtual machines to available site 2 hosts
Secondary Site failure
  • Replication between P-VOL and S-VOL stop with P-VOL suspending replication due to error condition (PSUE) and S-VOL in a suspended read-only state (SSUS)
  • Failover does not occur
  • I/O continues to active P-VOL paths
VMware High Availability fails over virtual machines to available site 1 hosts
 

For more information about Hitachi products and services, contact your sales representative or authorized Hitachi TrueNorth™ Partner or visit the Hitachi Data Systems website.

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