IRIS Volume Manager

Silicon Graphics IRIS Volume Manager(tm) is a powerful on-line mass storage management system for the CHALLENGE- and Onyx(tm) series of high performance servers and workstations. Based on the VxVM(tm) Volume Manager and VxVA (tm) Visual Administrator from VERITAS (tm) Software Corporation, IRIS Volume Manager has been enhanced to take advantage of Silicon Graphics POWERpath-2 (tm) parallel RISC architecture and powerful IRIX (r) operating system. IRIX is a fully symmetric multiprocessing implementation of UNIX (r) System V Release 4.

IRIS Volume Manager provides technical users with sophisticated disk management tools previously available only in mainframe OLTP environments. Through its implementation of virtual disks, IRIS Volume Manager gives system managers a wide range of options that improve the availability and performance of critical files and databases. Virtual disks eliminate the physical limitations of disk hardware by providing important features such as mirroring, striping, and spanning. The IRIS Volume Manager on-line performance monitoring and management utilities allow systems managers to tune the system for maximum performance without disrupting users or applications.

IRIS Volume Manager brings the technology of high productivity, user extensible, graphical interfaces to the world of system administration. For expert administrators, IRIS Volume Manager works hand-in-hand with familiar IRIX utilities and acts as a highly effective display for disk and file system management. For the less expert administrators, IRIS Volume Manager acts as a safe, simple, and effective guide in the world of disk subsystem management, allowing them to manage more complex configurations. The result is better informed and more effective decisions concerning disk-resource management that improve database and file system operation.

Key Features

Virtual Disk Environment

IRIS Volume Manager implements the concept of virtual disk devices, which are modeled after physical disk devices. The system administrator defines virtual disk "volumes" to be accessed by the system and applications as though the volumes were a linear address space on a formatted physical disk drive. An IRIS Volume Manager volume consists of plexes and subdisks. A volume may have one to eight plexes, each of which is a copy (mirror) of the volume\"s address space. Each plex comprises one to two hundred and fifty-six subdisks, which are portions of physical disks. IRIS Volume Manager combines subdisks into plexes in order to form volumes.

Support for Mirrored and Multidisk File Systems

With IRIS Volume Manager, file systems are mapped to volumes, which are themselves mapped to portions of one or more physical disks. This virtual disk approach enables volumes to be spread across multiple disks, be larger than any one disk, and have mirrored copies maintained. File systems are then associated with a particular volume. If the volume has three plexes, then three copies of the file system will be automatically maintained.

Mirroring can be done on a selective basis so that only critical volumes or portions of critical volumes need to be mirrored. This fine-grained mirroring is more economical than mirroring entire disks.

On-line Administration, Reconfiguration, and Backup

With IRIS Volume Manager, the system administrator may create, modify, or move any virtual disk structure without interrupting system operation. Examples of administrative tasks include creating the initial IRIS Volume Manager system, rearranging volumes on or across disks, and creating or deleting plexes (copies) of volumes and their associated file systems. On-line administration avoids computer downtime or reinstallation of the operating system when reconfiguring the system.

Using IRIS Volume Manager, the system administrator can also perform file system snapshot backups without interrupting service. Plexes can be brought off-line, backed up, and then updated without interrupting any applications accessing file systems associated with the plexes.

Automatic, Uninterrupted, On-line Recovery from Disk Subsystem Failures

The IRIS Volume Manager plex management and on-line administration work together to provide transparent protection from disk subsystem failure. When a failure occurs, IRIS Volume Manager automatically redirects all disk 1/0 to the surviving plexes without application interruption. The system administrator is then notified so the failure can be resolved.

Once the failure has been repaired, IRIS Volume Manager revives the failed disk by initiating whatever disk operations are required to make the failed plex consistent with its mirrors. This recovery operation is performed without system interruption.

Since the recovery process may involve significant disk 1/0, IRIS Volume Manager allows the system administrator to specify the appropriate recovery rate given the magnitude of the data and applications involved. This flexibility can either force high-priority recoveries to happen immediately, or specify a slower pace, which will have less impact on the 1/0 bandwidth of the system. In some failure cases, IRIS Volume Manager can resolve the problem automatically by rewriting the problem subdisk after a read failure. This returns the system to normal operating condition without requiring any operator-involved repair. In all cases, errors can be logged for later review.

Increased System Performance

IRIS Volume Manager-based disk and file management systems improves disk subsystem performance in many ways. By allowing a volume to span multiple disks, an IRIS Volume Manager system invokes parallel reads for the same file and increases disk 1/0 throughput. This capability, in the form of spanning or striping, can be customized to the particular application\"s 1/0 characteristics. Striping is effective for both reads and writes, particularly for random access oriented applications. Similarly, multiple plexes can be accessed in parallel to improve read operations. IRIS Volume Manager allows the administrator to choose the best disk organization for the application.

IRIS Volume Manager also provides mechanisms for performance analysis for system tuning. Device utilization or performance analysis can be accomplished via general 1/0 statistics or detailed logs. The analysis can involve any components of the IRIS Volume Manager system. The 1/0 statistics allow general identification of problems. A complete trace of all 1/0 activity can be done on a per volume basis for use in detailed performance studies or simulations.

An analysis can identify inefficient configurations, read/write bottlenecks, or unused resources. Examples include keeping track of read-to- write ratios and identifying hot spots where an unusually large amount of activity is taking place so that better mirroring or striping configurations can be identified. Such analysis helps the administrator determine how to tune the system to maximize disk-access performance or determine the most critical areas for high-availability protection.

Compatible, Customizable, and Future-protected

IRIS Volume Manager is installable on all Silicon Graphics CHALLENGE and Onyx systems running IRIX 5.0 or greater and on all POWER Series systems running IRIX 4.0.5 or greater.

Application programs operate on volumes using existing IRIX interfaces, so modifications to existing software applications are unnecessary.

IRIX file systems or other kernel components operate transparently on volumes through the block and character device switches. For example, once IRIS Volume Manager is installed, existing IRIX file systems or databases can then be easily striped or mirrored across multiple disks.

The IRIS Volume Manager environment can be easily customized via administrator control over various read/write policies, error handling policies, and the addition of volume usage types. Migration to future operating system environments is straightforward because IRIS Volume Manager is implemented primarily in the application level with minimum IRIX kernel-integration requirements.

Displaying Complex Information

IRIS Volume Manager uses a Motif (tm) graphical user interface and normal windowing techniques for control of administrator interaction. These techniques include the use of icons, mouse input, color, shading, patterns, and context sensitive help.

Although IRIS Volume Manager uses default settings for how and which information is displayed, each user can customize the display for specific needs. The user has full control over the display of information such as icon sizes, textual data included, and color usage, as well as magnification and scrolling to support the display of all data associated with large configurations. IRIS Volume Manager recalls each user preference whenever that user accesses the software.

IRIS Volume Manager provides a vehicle for displaying the relationships between physical disks and logical volumes. Selecting Disks displays each physical disk in the system, and the user can easily view which volumes, plexes, and file systems are related to each physical disk.

Selecting Volumes produces the same information, but begins with file systems and volumes, and permits the user to expose the structure that supports them. Both views can be displayed in parallel.

Most important, the user can create specialized views of the disks and file systems. These user-created views may combine the physical and logical views to display information most relevant at the time. These customized views are continually maintained by IRIS Volume Manager.

Changing Disk Subsystem Configurations

Through the configuration mode, the user may create, modify, or delete virtual disk (volume) configurations. File systems, databases, or other applications then use the volumes as if they were physical disks. Modifications can be initially prototyped and checked by IRIS Volume Manager for consistency before actually making configuration changes. Less expert users can be restricted by IRIS Volume Manager-enforced guidelines to minimize configuration errors. Expert users can override these guidelines.

Examples of configuration actions include creating the initial system, rearranging volumes on or across disks, including striping, and creating or deleting plexes (copies) of volumes. Modifications may involve using both the physical and logical views of the system simultaneously.

Modification actions also serve to recover from file or disk system problems, or to prepare for backups or archiving of data. Plexes can be brought off-line for backup and later revived to ensure consistency. All of this activity can be accomplished on-line, with no disruption of system operation.

Analyzing the Disk and File System

Environment IRIS Volume Manager provides analysis facilities to isolate bottlenecks or tune disk subsystem performance. Data for analysis is obtained from either volume driver statistics or traces of read and write events. Multiple analyses may _ run in parallel, and the user may add custom analysis routines to the IRIS Volume Manager environment.

Analysis involves any or all views of the system. Such views are by physical disk, subdisks, partitions, plexes, or volumes. The analytical data can be displayed graphically and monitored on line. The data is sampled and updated on the screen at a user-selectable rate. The user can keep track of read-to-write ratios to identify hot spots by having various icons colored differently depending on the percentage of time that the structure is busy. Such an analysis can identify inefficient configurations or unused resources and help the administrator determine how to tune the system to maximize disk-access performance or determine the most critical areas for high-availability protection.

Powerful Storage Control for Complex Computing Environments

With its flexible user interface and advanced disk storage control facilities, IRIS Volume Manager is the ideal tool for managing large file servers and database servers in today\"s distributed networks. IRIS Volume Manager is a simple and cost-effective way to maximize disk subsystem value while reducing overall computer operating costs. IRIS Volume Manager comes with comprehensive user documentation and software support is available from Silicon Graphics service offices worldwide.