Shared file systems help justify SANs

PolyServe, SGI enter the market

By Dave Simpson

Although storage area networks (SANs) allow users to share storage resources, without a shared (or clustered) file system, users can't actually share data. One of the key advantages of shared file systems is that they allow multiple users or platforms to read and write to the same file or disk volume concurrently. In some cases, the file systems support heterogeneous platforms.

PolyServe and SGI recently entered the market with the Matrix Server and CXFS file systems, respectively. They will compete to varying degrees with existing file system software from vendors such as ADIC, IBM/Tivoli, Sanbolic, Sistina, Sun, and Veritas.

PolyServe refers to its Matrix Server as a clustered file system, although vendors often use the terms "clustered" and "shared" interchangeably. Matrix Server can be combined with PolyServe's Matrix HA high-availability fail-over software, which the company has been shipping for about two years.

"We're fulfilling the promise of SANs, because SANs don't allow true data sharing where multiple platforms can simultaneously access the same files," says Mike Stankey, PolyServe's president and CEO. "Concurrent access to shared volumes also allows you to provision applications into the SAN and then dynamically allocate servers to the applications on an as-needed basis."

For now, Matrix Server works only with Linux on Intel-based servers, but PolyServe plans to support Windows early next year, according to Stankey.

Unlike other shared file systems that are based on a master server that runs the file system and provides data sharing to other servers, Matrix Server is a symmetric implementation in which each node has direct access to the shared disks. According to Stankey, this is the main differentiator between Matrix Server and most other file systems. PolyServe identifies its primary competitors as Sistina's Linux-based Global File System (GFS) and Veritas' Solaris-based Cluster File System (CFS) and SANPoint Foundation Suite HA software.

PolyServe has a formal co-marketing agreement with Hewlett-Packard and informal agreements with Dell, IBM, and Oracle. (Matrix Server supports Oracle9i Real Application Clusters.) PolyServe positions its file system running on clusters of Intel servers against large, monolithic servers from vendors such as Sun.

Bundled with PolyServe's Matrix HA software, Matrix Server is priced at $6,000 per CPU.

SGI goes heterogeneous
SGI last month delivered a version of its CXFS shared file system software that supports heterogeneous platforms, including Solaris and Windows NT. Previous versions of CXFS, which was introduced in 1999, supported only SGI's IRIX operating system.

For users, the primary benefit is the ability for multiple systems to directly access a single, shared 64-bit file system in a SAN environment. Users on different platforms can access the same file simultaneously, potentially eliminating the need to replicate files.

Bob Murphy, SGI's marketing manager for storage, claims advantages over existing shared file systems primarily in the areas of performance, journaling, and fail-over support.

According to Murphy, CXFS 2.1 is geared toward SAN environments with very large file sizes, which constitute SGI's traditional customer base.

SGI partner Hitachi Ltd. (which resells CXFS in Japan) plans to port the file system to HP-UX, AIX, and 32-bit Linux, but has not announced delivery time frames. SGI plans to port CXFS to Windows 2000 and XP in the third quarter, and to 64-bit Linux by early next year, according to Murphy.

CXFS 2.1 for Windows NT is priced from $1,800 for up to two processors and scales up to four processors. A version for Solaris is priced from $4,200 for up to two processors and scales to 108 CPUs. CXFS for IRIX is priced from $3,500 for one or two processors and scales to 512 CPUs.

SGI also introduced a bundled server—SAN Server 1000—that includes CXFS 2.1, a Fibre Channel switch from Brocade, and storage subsystems from LSI Logic. Pricing for the server starts at $173,000 for a configuration with 730GB and support for up to six CXFS clients.

This article was originally published on July 01, 2002