Symantec FileStore: Introduction to Scalable NAS for the Enterprise
Introduction
This document provides a technical introduction to and outlines the various use cases for the Symantec FileStore product. FileStore is a high-performance, highly scalable clustered NAS solution, delivered in a software appliance-style packaging. Taking advantage of the rock-solid stability of the Storage Foundation Cluster File System (CFS), FileStore delivers NFS and CIFS-based file serving, along with integrated storage tiering and other high-end NAS functionality. As a clustered NAS product, FileStore has a singular function: to share out unstructured file data in a simple-to-operate, highly scalable, and highly available manner. FileStore provides a simple, appliance-like administration model for file serving. This document describes a technical overview of Symantec FileStore and the benefits to deploying the product in a file serving environment.
Symantec FileStore Overview
Symantec FileStore is a fixed function, soft appliance that leverages Veritas Storage Foundation technology, including using CFS as a core file system engine and Veritas Cluster Server (VCS) cluster technology to allow seamless scaling of the FileStore cluster. The applications consuming the storage are running a standard NFS or CIFS-based client. Components of FileStore include the underlying, hardened Linux operating system, Storage Foundation CFS, and the new FileStore platform– all provided on a single DVD image.
Gateway Model
Symantec FileStore is built on a NAS gateway architecture model. The FileStore software can be installed on an industry standard sever running Intel Xeon-based processor architectures. These servers can be blade or other form factors.
The FileStore servers are then attached via Fibre Channel to FC-attached storage. This can be separate FC storage connected through a commodity switch (or point-to-point in a two-node cluster), or connected to and part of a much larger SAN. In all cases, the connections are made via one or more FC HBAs in each of the FileStore nodes. Thus the solution is an open storage offering allowing a high degree of flexibility in configuration. Customers can attach different storage devices to the FileStore cluster ranging from commodity storage to high-end arrays. Support for nearly all storage arrays that present valid SCSI-3 LUNs is provided, and there is additional support for active/active arrays through the Storage Foundation Dynamic Multi-Pathing software. Full details on this support can be found in the Storage Foundation Hardware Compatibility List, obtainable through the Symantec support website.
Figure 1 shows the conceptual model of a clustered gateway model. The diagram shows the front end IP network to handle NFS client requests and the backend heterogeneous Fibre Channel based storage tier.
Figure 1 Clustered Gateway Model
Leveraging core strengths
In addition to the Symantec FileStore platform itself, FileStore also leverages the capabilities and strengths of the core CFS file system engine and Veritas Cluster Server HA capabilities. Some of these key features include Dynamic Multi-pathing (DMP), the cluster file system (CFS), Veritas Cluster Server (VCS) and Dynamic Storage tiering (DST). Each of these layers represents industry-leading technology solutions and when combined into a file serving appliance provide an incredibly robust foundation on which to host file services.
CFS is the underlying core file system technology that is used within FileStore. CFS itself is built upon the industry-leading Veritas File System (VxFS). CFS provides full POSIX compliance; cache consistency across multiple nodes, a single namespace and a global lock management implementation. CFS also distributes load across FileStore cluster nodes so that both data and meta-data operations can be performed for the same file system across the cluster. This leads to near-linear scalability in terms of NFS operations per second. Leveraging the maturity and scalability of CFS was critical for the FileStore product in order to be able to ensure the mission-critical and rock-solid performance and availability that is expected in today‟s high performance storage environments.
DMP provides advanced FC HBA load balancing policies and tight integration with array vendors to provide in-depth failure detection and path failover logic. DMP itself is a large technical differentiator when evaluating FileStore against similar offerings from other vendors as it contains the most advanced capabilities of any multi-pathing driver in the industry.
Finally, VCS itself is used within FileStore to provide cluster wide monitoring, communication, and failover for all nodes and their associated critical resources including virtual IP addressing failover for both NFS and CIFS client connections.
Symantec FileStore platform components
The following section outlines the modular components that come together to form the Symantec FileStore platform architecture.
Installation
The first node in an FileStore cluster is booted from a single DVD containing the OS image, and FileStore software stack which is comprised of: The Storage Foundation Cluster Volume Manager, Storage Foundation Cluster File System, and the Storage Foundation Scalable File Server platform. Once this node is up and running the rest of the nodes in the cluster (defined via IP addresses during the first node boot up) are automatically installed over the FileStore private network with all necessary components (these nodes can also be imaged and installed at a later date). Key FileStore services are then automatically started to allow the cluster to begin discovering storage and creating NFS or CIFS shares.
Administration
Symantec FileStore contains a role-based administration model consisting of three key roles: Storage, Master, and Network. This delineation is consistent with the operational roles in many data centers. For each role the administrator accesses an easy-to-use Command Line Interface (CLI). This CLI provides for a common and consistent access method to all aspects of FileStore administration, including managing storage, creating shares, administering network interfaces, etc. Furthermore, an administrator can simply log in as one of those roles on the console node within the cluster (normally the first node that was installed) and can then execute commands which perform tasks uniformly on all nodes in the cluster.
A specific design goal of the FileStore product is that there should be no requirement to have any knowledge of Veritas Storage Foundation technology to install or administer the NAS cluster. In fact, there is no need to have any specific understanding of any Veritas technology, as the Symantec FileStore CLI masks any of the components and provides a single point of administration for the entire cluster. Of course, it should also be noted that users currently familiar with Storage Foundation technology will find familiarity with the basic management concepts of FileStore.
Adding or removing nodes from the FileStore cluster is a simple non-disruptive operation and is highly automated following the installation model outlined above.
NFS File Sharing and Lock Management (NLM)
FileStore provides for active/active shared data NFS file sharing across all nodes within the storage cluster. This provides for unparalleled scalability as clients are free to access any node within the cluster at any time, and be able to access the same data – both read and write. This allows for the ability to load-balance across a FileStore cluster by dividing access to specific nodes, and also allows the administrator to perform manual load-balancing correction by moving Virtual IP addresses between the storage cluster, when needed.
Because NFS can be shared read/write across all nodes, FileStore has a fully implemented NFS NLM module which allows a customer to use NFS advisory client locking in parallel with core CFS Global Lock management. The module consists of failing over the locks amongst the cluster nodes as well as forwarding all NFS client lock requests to a single NFS lock master. The result is that no data corruption will occur if a user or application needs to use NFS client locking with a FileStore cluster.
Figure 2 below depicts the architecture components of the FileStore stack. Figure 2
Figure 2 FileStore Component Architecture
CIFS-based file sharing
CIFS file sharing is made possible in FileStore with the use of the open-source Samba file sharing package. Within an FileStore cluster, all nodes can be running and sharing data over CIFS; further, CIFS shares can be failed-over to other nodes in the cluster, and the DFS referral functionality can also be utilized in order to span CIFS shares across all nodes, e.g. in a Homedirs environment. Full integration with Active Directory is also provided.
FTP-based file sharing
FTP file sharing is provided as a core feature of the Symantec FileStore product. Within the cluster, all nodes can be running and sharing files over FTP, allowing aggregate bandwidth of all FileStore nodes within the cluster. For bandwidth intensive tasks such as media streaming, allowing all FTP nodes to share the same data via both GET/PUT (read/write) provides maximum utilization from each node.
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