Take a Byte Out of Your Storage Problems

Continued from last week

THE SAN ZONE AND OTHER MANAGEMENT TECHNOLOGIES

In fact, you could say that the ultimate cost of deploying and managing a SAN is a function of that SAN's complexity. Most SAN systems and some SAN devices--such as switches and hubs--include management software. With this software, you can use technologies such as Logical Unit Number (LUN) masking, SAN zoning, or storage virtualization to manage storage for heterogeneous networks.

As you probably know, SCSI buses use LUNs to identify peripheral devices (such as DAS devices) that are attached to computers. Some Fibre Channel devices--such as host bus adapters (HBAs)--enable you to map LUNs to specific blocks of storage. Fibre Channel devices (such as RAID controllers) that support LUN masking can then use these LUNs to ensure that a particular server sees only the LUNs that are assigned to it.

Like LUN masking, SAN zoning enables you to carve out blocks of storage for particular servers or applications. Using Fibre Channel devices that support SAN zoning, you can group servers or applications that share storage into a zone. These servers and applications can then see only the storage that resides in that zone.

As you may imagine, carving out storage using individual devices such as HBAs, hubs, and switches can be complicated, time-consuming, and costly. Consequently, many companies offer software to simplify these management tasks. For example, the XIOtech REDI storage management suites use storage virtualization to enable you to carve out and manage storage for one or more XIOtech MAGNITUDE SAN systems.

As Dick Blaschke, VP (Marketing). XIOtech, explains, when XIOtech says its management software virtualizes storage, it "simply means that the device characteristics of the disk drives are completely transparent to the administrator, which means you can now manage space rather than disk drives."

On the other hand, EMC Enterprise Storage Network (ESN) Manager uses SAN zoning to enable you to configure access to storage on its Symmetrix SAN systems and to storage on Compaq, HP, and Hitachi SAN systems.

However, for the most part, the storage management software you purchase to help manage storage on a particular SAN system works only for that system. If your company's SAN solution includes SAN systems from several different companies, you must manage storage on each of these systems separately. To further complicate the SAN management matter, not all SAN management software supports all SAN devices. For example, SAN management software often does not support all major Fibre Channel switches and hubs.

To prevent this potential management problem, you can choose a particular SAN system and stick with that system. For example, you can use REDI SAN Links and REDI SAN Link Replicator to manage several MAGNITUDE systems.

BRIDGING THE SAN GAP

In the near future, you will also be able to prevent many SAN management problems by using NetWare 6 and Novell Cluster Services 1.6 to manage storage on your company's SAN. As you may know, NetWare 6 includes Novell Native File Access components. These components enable users and applications to use any of several file-sharing protocols to access files stored on a NetWare server. For example, an application running on a Windows NT server can use the Common Internet File System (CIFS) protocol to access storage on a NetWare 6 server. To do this, you simply "map a drive from an NT server to storage on a NetWare 6 server," explains Dan Lawyer, Novell product manager.

NetWare 6 also includes Novell Storage Services (NSS) 3.0, which uses NSS storage pools and logical volumes to virtualize storage management for a NetWare 6 server. NSS storage pools are areas of storage collected from one or more storage devices. Logical volumes, which expand and contract according to the amount of storage they are actually consuming, are built upon these storage pools.

NSS 3.0 enables you to extend NSS storage management from a single server to up to 32 servers--all of which can then share storage on one or more SAN systems. NSS 3.0 includes a flag that marks a storage pool as sharable for clustering. When you set this flag, NSS 3.0 cannot activate a storage pool unless Novell Cluster Services 1.6 is running on the server.

Novell Cluster Services 1.6 then uses a Novell technology called the Cluster Volume Broker to grant or deny access to storage. To prevent one node from corrupting another node's data, the Cluster Volume Broker allows only one node in the cluster to access the volumes on a storage pool at a time. Novell includes the Cluster Volume Broker in Novell Cluster Services 1.6 rather than ffering this type of technology as a standalone product, as other companies do.

You can use Novell Cluster Services 1.6 to manage storage for various network operating systems simply by hosting Novell's renowned file and print services on a NetWare cluster. You can then map drives from servers and clients to this NetWare cluster, which accesses and stores the requested data on the SAN. For example, you can map drives from Windows 2000 and NT clients and servers, or you can mount UNIX and Macintosh volumes.

Furthermore, because NSS 3.0 storage pools can draw storage from one or several storage devices, NetWare 6 and Novell Cluster Services 1.6 can manage SAN storage across one or several different types of SAN systems.

You can also manage SAN storage to a lesser degree today using NetWare 5.1 and Novell Cluster Services 1.0.1, which the Texas Office of the Attorney General (OAG) demonstrates with its new SAN implementation. The Texas OAG is currently using these versions of NetWare and Novell Cluster Services to manage SAN storage for GroupWise and NetWare file and print

services.

CONCLUSION

Did you notice that you can use Novell Cluster Services 1.6 and NetWare 6 to manage both file-level and block-level storage? That's because Novell Cluster Services 1.6 and NSS 3.0 can virtualize the type of storage that SANs provide as well as the physical devices that comprise that storage--at least as far as NetWare storage is concerned.

As the information age progresses, technologies that virtualize--or blur the distinctions between--particular types of storage will continue to emerge. In the end, one storage solution may fit all. In the meantime, however, you may need to deploy a combination of storage solutions to manage your company's ballooning storage needs.

For example, if your company needs both block-level and file-level storage, you may need to deploy both a NAS and a SAN. On the other hand, if your company is already storing a large amount of old data and is generating vast amounts of new data every day, you may want to consider having an SSP store only the new data.

In other words, until a one-size-fits-all storage solution emerges, your company's storage solution will probably end up being as unique as your company's storage needs are.

Cheryl Walton works for Niche Associates

Reprinted with the permission of Novell Connection