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TechNote:
Clustered File Systems
The availability of clustered file systems has dramatically enhanced the ability to provide shared file-level access to SAN-based storage. Clustered file systems enable SAN-connected workgroups to share concurrent, direct, high-performance access to storage resources on a SAN. In other applications, clustered file systems are useful for web-server farms, and enabling SAN-based, LAN-free HSM installations.
InfraStor has evaluated a number of newer approaches to the needs for shared access to files through direct SAN connections, where an alternative to NAS is desired for performance reasons.
For a mixed OS environment, ADIC's StorNext File System is recommended. It has powerful capabilities for access to very large data stores, and supports a variety of OS's including Windows, Solaris, Linux, IRIX and AIX. One device must be designated as an MDC (Meta Data Controller). In the Windows environment, the MDC can be a Windows machine, but for failover redundancy of the MDC, it must be either a Linux or Solaris machine.
An ADIC case study is available that describes InfraStor's installation of StorNext in a 40TB SAN environment along with an ADIC Scalar 10K, 250TB tape library. Together the file system and the companion ADIC product StorNext Data Management Suite provide a high-performance HSM function.
SGI's CXFS is a similar clustered file system, supporting a number of O/S's, including recently announced support for MAC OS-X. The MDC must be an IRIX (SGI system). A white-paper on the CXFS technology is available.
For open systems, an attractive alternative is a product from Sanbolic called Melio. It is a true clustered (global) journaling file system. The product is simple to install, operates transparently and does not require that a master MDC be designated on the SAN. Today, Melio supports Windows only, but a roadmap exists for Unix flavor support.
In the Media and Electronic Pre-Press worlds, where Apple MAC support is often a need, there are a number of options depending on the requirement for OS-X support. Apple Computer's X-SAN product allows file-level shared access and is compatible with StorNext.
The following products are not true "Clustered File Systems", but do offer SAN-based volume or file sharing between systems with a common SAN connection to a storage resource:
Charismac's Fibre-Share is not a true clustered or global file system but allows shared access to volumes rather than individual files. Charismac plans to offer a plug-in to allow Macintosh HFS volumes to be mounted and accessed under Windows NT. Fibre-Share for the MAC can also mount OS/9 file systems in addition to OS-X, making it the only cross-platform MAC OS-X compatible option today.
Tivoli-IBM's SANergy allows multi-OS shared access files on a SAN. While still available, SANergy has now largely been superceded by IBM's TotalStorage SAN File System that allows concurrent control of writes in a shared volume to the file-level in either NTFS or NFS file systems. As in other systems, one or more MDC's are defined that mount the shared volume directly. The clients have a SAN connection to the volume and a TCP/IP connection to the MDC, but mount the volume as a network share. Hardware requirements are IBM-centric. Supports Windows 2000, AIX and Linux (beta).
Key Product Summary
Clustered File Systems:
- ADIC's StorNext
- SGI's CXFS
- Sanbolic's Melio
- IBM's SAN File System
Volume Sharing and Redirector Software:
- CharisMac's FibreShare
- Tivoli's SANergy