BEST PRACTICES GUIDE: Nimble Storage Best Practices for Scale-Out

(1)

BEST PRACTICES GUIDE:

(2)

Introduction

Nimble Storage scale-out cluster functionality allows scaling of performance and capacity beyond the limits of a single array, while maintaining the management simplicity of a single array. Adding multiple arrays into the cluster linearly increases both performance and capacity, while leveraging the resources of all arrays in the cluster. Scale-out storage is ideal for IT environments looking to eliminate individual silos of storage across their infrastructure. Multiple types and generations of arrays can be combined in a single Nimble Storage cluster, protecting your investment.

This document walks through the planning, hosting, and networking best practices associated with Nimble Storage’s scale-out cluster.

Terminology

Scale-Out Cluster: Multiple Nimble Storage arrays that are combined together and managed as a single logical storage entity.

Storage Pool: A pool is a logical collection of one or more arrays in a cluster containing volumes and their respective snapshots and clones. Volumes within a pool are striped across all the pool member arrays.

Storage Array: Arrays are a highly available purpose-built storage appliance that consists of redundant storage controllers, disks and solid state flash storage.

Planning Scale-Out Clusters and Pools

Nimble Storage provides a rich set of features associated with scale-out clustering around data rebalancing, migration and host integration to get the most out of your investment. The following section features best practices and suggestions to follow when planning your deployment.

Cluster Arrays Based on Management Boundaries

(4)

Cluster boundaries can also make sense for organizational boundaries to keep data assets separate. Creating separate scale-out clusters of arrays might also make sense for sensitive data such as finance and human resources to meet security audit requirements. If you require more granular array grouping then you should use separate Storage Pools.

Adding, Removing and Merging Scale-Out Cluster Arrays

Changing cluster membership is a quick process that makes storage performance and capacity available immediately, or removes it entirely. Moreover, it is transparent to hosts – i.e. there is no downtime for hosts or applications. However, it is important to understand that changing pool membership can take time while the existing data volume, snapshots and clones are rebalanced on the resulting pool arrays. For example, if you would like to remove an array from a cluster, then you should first evacuate it from its’ current storage pool to migrate data to the remaining pool members. Merging scale-out clusters is a quick process because it doesn’t require any immediate data rebalancing; however this process may be followed by migrating volumes between pools or merging pools which does result in data rebalancing across the member arrays.

For further information about the rebalancing process, please see the following section titled “Pool Rebalancing” to fully understand the time associated with cluster and pool management.

Pooling Arrays within a Scale-Out Cluster

(5)

Pool Arrays for Consolidation and Fault Isolation

Nimble Storage scale-out clusters allow you to pool whole arrays to consolidate storage based on logical boundaries. Pooling storage can be helpful for departmental chargebacks, fault isolation between production and non-production environments, or by application. Nimble’s scaling and migration technology eliminates planned downtime when storage pools are changed.

Pool Arrays with the Same Storage Capacity

(6)

across all arrays. Placing arrays with significantly differing capacity within the same pool may not fully utilize the performance resources available in the pool. By creating pools that span arrays of similar capacity, performance is balanced equally across all arrays in the pool which maximizes utilization of all performance resources.

Pool Rebalancing

Nimble Storage pools are rebalanced when storage objects such as arrays, pools and volumes are added, removed or merged. Rebalancing is a non-disruptive low-impact process that allows application I/O to continue uninterrupted even to the data sets being migration. Pool rebalancing gives highest priority to active data I/O and performs the rebalancing process with a lower priority. The relative speed of rebalancing is dependent upon the use case being performed and how quickly a typical user would expect the procedure to complete.

Non-Disruptive Pool Rebalancing Use Cases

Volume Migration - Volumes can be selectively migrated between pools including their associated snapshots. Volumes support read/write during the migration process.

Adding Arrays to a Pool - Add

performance and storage capacity to an existing pool.

Evacuating Pools - Remove an array from a pool when it’s no longer needed or when it is being replaced by another array. There must be enough capacity

(7)

within the remaining pool members to accommodate the volumes and snapshots migrated from the evacuating pool member.

Merging Pools - Useful when combining storage resources that were previously in separate pools thus increasing performance scaling across multiple arrays.

Networking Best Practices

(8)

SAN Bandwidth Availability

Nimble Storage scale-out clusters perform communication between arrays to coordinate production I/O in-addition to performing rebalancing of data between arrays. The intra-SAN communication and data migration is designed to be a low-impact process that won’t interfere with production I/O. However, the amount of available SAN bandwidth will impact the speed with which volume migration and pool rebalancing can take place.

Cluster Arrays on the same Subnets

All of the arrays within the same Group must be able to see the same sub-networks. This ensures that host connectivity follows the proper network pathing as well as to ensure that volume and pool migration works properly and with maximum performance.

Choosing iSCSI Switches

Network switches provide a critical part of an iSCSI storage area network. There are many different classifications of switches and it is important to understand the characteristics that make a switch good for supporting iSCSI storage traffic. Use the following table when evaluating network switches:

Non-blocking Backplane A switch used for iSCSI data communication should have a backplane that provides enough bandwidth to support full duplex connectivity for all ports at the same time. For example, a 24 port Gigabit switch backplane should provide at least 48 Gigabits per second of bandwidth or (1 Gbps * 2 for Full Duplex * 24 Ports).

Flow Control (802.3x) Flow control provides a mechanism for

temporarily pausing the transmission of data on Ethernet networks when a sending node transmits data faster than the receiving node can accept it. You should enable flow control on all hosts, switch, and array ports to ensure graceful communication between network nodes. Nimble Storage array NICs have flow control enabled by default.

(9)

full performance between connected nodes. Support for Jumbo Frames Ethernet frames that transport data are typically

1,500 Bytes in size. While this does a good job of balancing application network traffic between network clients and servers, while host to storage communication tends to be measured in Kilobytes. Jumbo frames were created to better handle the flow of iSCSI SAN traffic and consist of 9,000 Byte frames. Enable Jumbo frames to improve storage throughput and reduce latency.

Can Disable Unicast Storm Control Storage traffic can appear bursty to switches which can be mistaken by some switches as a packet storm and blocked. Disabling Unicast Storm Control ensures that the storage traffic is transmitted unfettered.

Use Nimble CIM and PSP Provider for VMware Hosts

Nimble Storage provides scale-out network integration for VMware hosts using a CIM and PSP provider installed on each ESX host server. During installation, you specify the discovery IP of the scale-out cluster and the CIM connects to it for discovery of all possible network connections between each host and the arrays in the storage cluster. The CIM is then responsible for maintaining an optimal number of network sessions between the VMware ESX host and the storage array.

The Nimble PSP provider communicates with the scale-out cluster for each volume attached to its’ host to maintain a bitmap of the logical volume layout. The PSP uses the volume bitmap to direct I/O requests to the appropriate array using the paths maintained by the CIM provider. Nimble’s CIM and PSP providers will periodically update their network path and logical volume bitmaps with the arrays to maintain an optimal muti-path I/O (MPIO) strategy that maximizes performance.

Use Nimble Connection Manager on Windows Hosts

Connecting Microsoft Windows host servers to iSCSI volumes is a simple procedure for a single connection. However, creating connections to support Multi-Path I/O (MPIO) on many host servers can be a cumbersome process with many repetitive steps. Nimble Storage provides a solution called Connection Manager that integrates with Microsoft Windows hosts to provide MPIO

(10)

the appropriate network paths. NCM will create iSCSI connections for each host network interface card and each array in the group. Nimble Connection Manager leverages a logical volume map that permits quick direction of I/O requests based on the scale-out volume’s physical distribution between arrays. Nimble Connection Manager will periodically refresh the network pathing and logical volume bitmap to maximize storage performance.

Non-Windows/VMware Host Scale-out Connectivity

Host operating systems that do not have integration permitting third-party multi-path I/O direction can still use Nimble Storage scale-out features. Connections will need to be configured manually between host NIC ports and array NIC ports. If an I/O request reaches an array that cannot service it, then an iSCSI redirection is triggered to send the requestor to the appropriate array.

Getting Started

Get started on planning by performing a quick audit of your current applications and storage to understand how much storage capacity and performance is needed. Document how these applications are expected to grow over the next year, three years and five years. Also, document any specific requirements around management, high-availability and isolation for specific

workloads along with any additional requirements around data protection. These are good factors to incorporate in the initial design and deployment.

Nimble Storage provides the flexibility to scale-to-fit applications and workloads storage needs and a little planning upfront can help ensure a smooth deployment of a scale-out storage cluster for any and all data center needs – today and in the future.

Nimble Storage, Inc.