W2K file system lays storage foundation
By Zachary Shess
At the Windows 2000 launch last month in San Francisco, Microsoft and a variety of supporting vendors promised an operating system and certified software that will help improve storage-related functionality, reduce costs, and provide easier and more comprehensive management. Achieving these goals begins with file access and Windows NT File System (NTFS) version 5.0 and Microsoft Distributed File System (Dfs).
Microsoft added Dfs to Windows 2000 to unite files on different client machines within a LAN or WAN and to provide a uniform naming convention and mapping for groups of servers, shares, and files. Dfs specifically addresses issues related to network growth and remote data access. For expanding networks, mapping single drive letters to file-server shares is neither efficient nor scalable, and it is not suitable for users trying to access data stored in a growing number of locations on larger networks.
With Dfs, file servers and their shares are organized into a logical hierarchy, enabling better data organization and management.
By providing name transparency to disparate server volumes and shares, Dfs is no lon-ger tied to a single file protocol, supporting server, file shares, and file mapping regardless of the operating file client.
"A single view of all the networked file servers within an organization makes it much easier to find data stored on file shares or servers and to build a hierarchical file system whose contents are distributed through a WAN or LAN," says Mark Hassall, a Windows 2000 product manager at Microsoft.
The arrival of Windows 2000 also marks a new version of NTFS. Version 5.0 includes a wide-ranging mix of enhancements, which affect laptop users on up to system administrators. Distributed link tracking better monitors data movement by keeping shortcuts intact as requested files move to a new drive or computer system.
Additionally, administrators can control and monitor the amount of disk space used by individuals or groups through new user-transparent disk quotas. Quotas may be implemented to track or maintain limits on an individual basis for a specific NTFS volume. Through an updated file-system filter architecture, ISVs can build additional quota management tools onto existing built-in quotas.
The new NTFS Change Journal helps track changes to file volumes without complete rescans. The Change Journal describes and holds changes to files and directories within NTFS. Microsoft officials contend that this will lower I/O costs because applications such as backup tools, indexing services, and virus scanners don't have to rescan an entire volume to find changes. Instead, it's done once; changes are then learned from reviewing the journal.
Stacked just above NTFS and Dfs is the Logical Disk Manager (LDM), which is designed to provide increased flexibility, manageability, and availability. Licensed from Veritas Software, LDM is a scaled-down, Windows version of the Unix-based Veritas Volume Manager.
LDM enables disk RAID objects in RAID levels 0, 1, and 5 to be created, broken, and rebuilt online. File systems can also be extended over new partitions while the file system is running. As a result, performance and redundancy requirements can be reconfigured and the volume size extended without taking the system off-line. The volumes, which can be a stripe set, mirror set, or parity striping set, can be converted to a mirror set at any time, or a mirror can be removed from an existing mirror set without downtime.
Further storage reconfiguration facilitated through LDM includes the ability for LDM-managed disks to be self-describing and the ability to change SCSI IDs, LUNs, and host adapter ordering without compromising the system configuration.
product manager, Microsoft