Host-based clustered file systems
@25839 Clustered file systems that operate at the host level provide some distinct advantages over clustered storage systems and NAS gateway configurations:
Silicon Graphics Inc. (SGI) allows users to create a CFS by deploying agents for its InfiniteStorage Shared Filesystem CXFS on each host. With support for a wide range of operating systems, including IBM AIX, 32- and 64-bit Linux, Windows, Sun Solaris and Mac OS X, it allows any of these operating systems to access and share the same files. These files are also accessed using block-based protocols such as FC or iSCSI, which remove the processing overhead associated with NFS and CIFS that clustered NAS gateways and storage systems require.
To control access to the files and maintain their integrity, SGI uses a meta data server for each CXFS file system. This requires each server in the cluster to communicate with the meta data server over a TCP/IP link. Even though the amount of meta data traffic sent over this TCP/IP link is minimal, users may not want to put this meta data server on the same physical network to help minimize network collisions and provide higher uptime. Users in highly available environments may want to consider building another physical network and clustering two meta data servers--an expensive and complicated configuration--so the failure of a single meta data server doesn't bring down the entire cluster (see "Alternative storage clustering methods" this page).
Benefits vs. complexity
A CFS gives users the option to cluster storage at the host, network or array level to share file access and maximize storage utilization. Each clustering architecture has its limitations (see "Clustered file-system architecture pros and cons"), such as drive types or the need to install agents on hosts.
Assess your current storage environment and processing needs before jumping on the CFS bandwagon. Though the benefits may be substantial, you should also expect your storage environment to become more complicated and perhaps more difficult to manage.
- There's no need to purchase proprietary storage systems.
- They work in most mixed-vendor environments.
- There's no need to use a mix of file- and block-based protocols.
- The performance overhead associated with processing NFS and CIFS is minimized.
About the author: Jerome M. Wendt is a storage analyst specializing in the field of open-systems storage and SANs. He has managed storage for small- and large-sized organizations in this capacity.
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Three ways to create clustered storage, page 1.
This article first appeared in
Storage's September 2006 issue.
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