Persistent File System Technology

	Persistent File System Technology

	One of the areas of computing that has changed very little in the last 10 years is that of file-system technology and data management. File systems have evolved to support longer file names and security, but little else. As great strides have been made in storage capacities, the Internet, and computing speed, but little has been done with the basic element of all computers — whether on a PC, network, mass storage, or across the Internet. The Persistent File System (PFS) is a software technology that combines several file-system components to simplify access to mass-storage devices. PFS consolidates all file and folder information into a single file-system view. On a PC, PFS can gather information about all removable media (tape, removable hard disks, floppy disks, CD-R/RW discs, and most others) and consolidates all files and folders into a single file-system view by creating a virtual connection to all storage resources. PFS then presents itself to Windows as a logical device with standard drive-letter access, even though PFS is not, a physical device. The directory can be viewed and accessed whether the media is on-line or not. PFS' ability to view and consolidate directory information from various sources has been successfully adapted to distributed storage in 1Vision's ground-breaking vSERV NAS Module™ and vSERV™ Aggregated File System products. For this purpose, PFS has been streamlined for throughput across networks that serve a large number of users and manage terabytes of data. vSERV NAS Module gathers directory information from multiple network attached storage (NAS) devices and shares it among all devices within a defined resource group. vSERV does the same for systems comprised of Windows-based servers that may or may not include supplemental NAS devices. The result in both products is a single, aggregated directory comprised of the contents of each device's respective directory. All available resources appear as a single pool or resources regardless of where data resides on the network. In its use on the PC, the heart of PFS is its relational database that stores name-space information for all of the locally attached storage devices. The PFS database is not a passive file list. PFS incorporates Interceptor modules to gather name-space information from the storage devices and to provide virtual I/O functionality to the storage system. It is the Interceptor modules that make possible user access, through a standard drive letter, to all storage devices and removable media. Another major PFS component is the Information Management Process (IMP). An IMP is a task-specific, modular application that manages essential PFS functions, including configuration and database viewing tasks in addition to the movement of data from one device to another. As task-specific modules, IMPs add great flexibility and power to the PFS, which handles all information management tasks for the IMPs, without adding undue complexity or processor overhead. IMPs are implemented to take full advantage of the power of the PFS and the Interceptor modules. Figure 1 — Integration of Persistent File System with native file system (Patented) PFS technology was first introduced with the 1Disk™ product that provides drive-letter access to a dynamically created catalog of a user's removable media. This product greatly simplifies the organization and use of removable media. 1Disk's main IMP functionality is a viewer to simplify finding files and for configuration of the system. The second product to use PFS technology is 1Safe™ (OEMed as OnStream Echo™) software. 1Safe provides the user with a back up and restore IMP along with directory viewer functionality. Of course the PFS catalog drive-letter access is provided for access to all tapes used in the system (along with any other removable media). Additionally, PFS provides drive-letter access to the tape drive itself. PFS has also been adapted for use over the Internet in 1Vision's 1Disk.com, a software package for the management of online web storage. The most innovative use of PFS technology to date is its further adaptation to networked storage in the vSERV NAS Module product. A streamlined version of the original PFS enables communication between storage devices to share directory information. This essential component allows vSERV and vSERV NAS Module to collect and aggregate multiple directories across a particular domain. It is the power of PFS that sets vSERV and vSERV NAS Module apart from the ever-growing field of products claiming to pool storage resources. Each device to join the aggregated view must have the software installed for the PFS component to run its file system parallel to the appliance's individual file system. PFS replicates the system metadata and shares it with all participating appliances. The software translates the collective data into the aggregated directory view. The real power of PFS is that it does not affect the operation or rights of the native file system, but, rather, it extends and leverages the intelligence of the file system. Unlike Microsoft's Distributed File System (DFS), which requires any given level of a directory exist on a single physical server, vSERV and vSERV NAS Module span a directory across multiple devices, enabling their seamless addition. New devices' capacities are instantly added to a group's cumulative storage space. The entire process of increasing capacity is invisible to the end users, but is immediately available for their use. Although PFS itself is not OS dependent, the first release of vSERV and vSERV NAS Module are exclusively for Windows 2000 SE. The software honors all NTFS security and minimizes its impact on performance and stability. Access to vSERV and vSERV NAS Module storage inherits all of the underlying attributes of NTFS while remaining transparent to the end user and system administrator. Any change to the native file system is reflected in real time within the aggregated view. PFS is functional with other file systems such as UNIX and Linux. vSERV NAS Module can be loaded on a separate server, and be used to virtualize all the files on a group of legacy boxes with closed OS's such as Snap and NetApp. Access to all stored data using standard file-system access greatly simplifies how users retrieve files, whether it be on a PC, across the Internet, or to networked storage. The fact that PFS technology enables file retrieval in a natural fashion increases user satisfaction. Backup and basic media management were simply the first steps in applying PFS technology. Since the architecture of PFS is very extensible, as is the underlying database technology, a much richer data-management environment has been created. Concepts that were originally applied to local storage are successfully being extended to network and Internet servers. Due to its broad applicability and ease of use, PFS technology will become an integral part of the storage management industry.