SAN Management Software (SAN Intelligence)

Managing a large storage network requires robust configuration management. Strong monitoring capabilities are necessary to centrally manage widely dispersed storage resources. SAN management software must also be able to detect imminent failures, performance bottlenecks, and out-of-bound conditions by extrapolating from data provided by the network and storage devices, and to take predefined actions to deal with these events.

Managing a SAN requires combining two management disciplines: storage management and network management. Apart from the challenge of managing data in a SAN, managing the SAN's networking devices provides new challenges. Together, the different aspects of SAN management fall into the following components.

Administrative management: Includes centralized management and control of storage resources, as well as topology and configuration management and fault isolation for the hubs, switches, routers, and bridges that make up the SAN fabric. In time, industry-standard implementations of SNMP and Common Information Model (CIM) protocols are likely. In the meantime, the various vendors of SAN interconnect hardware products provide software that monitors and manages their own products.

Data management: Includes backup, archiving, data replication, hierarchical storage management (HSM), mirroring, and vaulting. (For a discussion of backup, see "SAN Applications" on page XX.) Legato, Veritas, Computer Associates, HP, Compaq, and IBM lead the development of data management software.

Storage Resource Management (SRM): Defines a class of management applications that monitor and manage physical and logical storage resources on a network to simplify administration and to ensure data availability. These resources include storage hardware such as disk devices and subsystems, tape and optical media, and libraries and jukeboxes. SRM products monitor the health, availability, performance, and configuration of storage systems to provide built-in policies and optimization advice. SRM also includes Capacity Management; Configuration Management; Data, Device, or media migration; Event/Alert Management; Policy Management; and Volume Management. SRM is an increasingly critical segment of the storage management market. Vendors include Highground, Legato, Sterling, Boole and Babbage (BMC), IBM, and Hewlett-Packard (HP).

Security Management: UNIX and NT give a server ownership of all visible storage. Since a SAN gives access to all storage connected to the fabric, some mechanism is required to prevent servers from overwriting one another. Today, one or all of three levels of security accomplish this protection: The first, the HBA level, binds an HBA to specific LUNs (logical units) and blocks visibility of all other LUNs in the storage pool-called "persistent binding." The second level can reside in the volume management software. You can implement the third level, called "access control," using port zoning, which divides the switch into logical zones. Legato, Brocade, and Ancor support access control, among others.

File Management: You can view and manage SAN data in two ways: as a set of disk blocks (raw data) at the physical-disk layer, or as a set of logical files at the logical-file layer. The difficulty with a heterogeneous-platform SAN lies in selecting an OS and a file system that can efficiently handle the various formats. When managed at the physical-disk layer, all the server systems sharing the data in the heterogeneous network must agree to use the same file-system format. It is highly unlikely that all the vendors will standardize on one on-disk file-system format. When managed at the logical-file system layer, essentially three alternatives exist, each leading to several possible variations.

· Select one of the hosts' OS and file system, say, Windows NT and NT File System (NTFS), and use agents within NT or each client's OS to convert the files from native NT format to the format each non-NT client OS expects. The problems with this approach are: the poor performance and efficiency in serving the non-NT platforms' UNIX files; the cost of writing client agents for each of the non-NT platforms needing support; and the practical lack of support for this kind of NT-centric approach from non-NT vendors.

· Layer software modules on top of, or underneath, one of the host OSs or file systems-modules that bring additional functionality and facilitate the transition. This approach has the advantage of providing a vendor-neutral solution to sharing. The problems with this kind of an approach include: the difficulty of agreeing on a new standard in this field in time to capture the market; the difficulty of providing clients for all of the potential host OSs required for adoption into a heterogeneous network; and the difficulty of providing a seamless integration, and of keeping up with new revisions of hosts' OS releases.

· Use a generic independent file system, sometimes referred to as a "distributed file system." The problem is the reluctance of system and network OS suppliers to agree on a standard. With this approach, you can maintain backward compatibility with the existing LAN marketplace and seamlessly integrated it into the emerging SAN marketplace. The Storage Network Industry Association's (SNIA) file system working group is currently studying this kind of approach.

In the meanwhile, several approaches resulting from the limitless imagination of some very talented engineers are being implemented. (Examples of vendors implementing such solutions are listed in "SAN Applications" on page XX.) The leading file-system suppliers are Veritas and CrosStor (previously Programmed Logic Corp.).

Where Will the SAN Intelligence Reside?

Many SAN components, including storage controllers for disk subsystems, some tape subsystems, and interconnecting hardware components, will have processing capability. Nearly all will have a view of the network topology, and most will have some sort of management
interface. All claim control over the Storage Network Manager.

Three major approaches for centralizing SAN intelligence suggest locating this intelligence in the disk storage system, in the Fibre Channel switch, or in an independent server connected to the SAN fabric. When interface standards exist, intelligence and management capability are likely to be widely dispersed in the storage network.

The Storage Subsystem

On the other side of the hubs and switches are the storage devices. They could be unintelligent disks, redundant array of inexpensive disk (RAID) devices with internal controllers designed to handle data mirroring and data striping, or highly intelligent storage servers with processors that run their own storage management software. Similarly, you can connect tape drives, optical drives, or libraries to the network. In the best possible scenario, the devices will connect to the network via Fibre Channel. You can also connect native SCSI devices to the network via a Fibre Channel-to-SCSI bridge. Using a bridge is common in early SAN implementations, especially with tape devices, as Fibre Channel tape drives and libraries have been slower to come to market than Fibre Channel disk.

By consolidating larger capacities, options that are otherwise prohibitively expensive become practical, permitting high levels of performance, scalability, and manageability. In addition to the vendors listed below under SAN-The Total Solution, vendors providing Fibre Channel disk-array subsystems include LSI, Artecon, and MTI, with Mylex leading the development of controllers. Tape libraries are offered by ADIC, ATL, HP, and StorageTek, among others.

SAN-The Total Solution

Just about every major storage vendor has previewed its SAN plans, and many suppliers have begun rolling out products. Although most storage vendors provide a few of the modules needed to build a SAN infrastructure, only a handful of vendors and systems suppliers have the breadth of undertaking to integrate, qualify, and support a full SAN implementation. Most SANs use components from different vendors or partners. Among the system suppliers that have announced their intention to support a total solution are HP, Sun Microsystems, IBM, Compaq, SGI, Amdahl, and Sequent. Independent vendors include EMC, StorageTek, MTI, 3Com, CNT, and McData. Unannounced at press time but known to have plans for total solutions are HDS and CLARiiON.

While the industry is fighting the major challenge of integrating the multiple pieces that must fit in a SAN solution, some vendors offer a condensed version of SAN they dub "SAN in a box." It's a totally integrated solution that includes a Fibre Channel switch with a number of ports, high-performance software, and the storage elements. "SAN in a box" is pretested and ready to run for specific applications, eliminating the installation and integration concerns. The negative side to this approach is that it limits you to one vendor for expansion and doesn't let you reuse existing assets. XIOtech offers one of the first fibre implementations of a "SAN in a box.", and Storage Coimputer implemented a SCSI version with logical switching.

By: Farid Neema

PERIPHERAL CONCEPTS, INC.
351 Hitchcock Way, Suite #B-200
Santa Barbara, California, 93105
Tel: (805) 563-9491
fneema@silcom.com

This article published in the May 1999 issue of Windows NT Magazine