Wide Range of Options for Storage Users

Tivoli's management environment seems an unlikely place to put replication, but evaluating a range of replication tools may give you a chance to define your requirements and shop around. An hour or more between replicas is not replication: It's disk-to-disk backup at a one-hour frequency. If you're backing up documents, one-hour intervals are probably fine. If you're backing up high-volume transactional data, such as databases and e-mail files, you'll probably want to look at CDP solutions. If you're handling backups for low-volume transactional data, near- real-time replication with support for "live backups" is probably your best bet.

The next question is where the replication should take place. Do you want it in your SAN arrays, your NAS devices, your SAN switches, independent appliances or standalone servers? This decision is largely dependent on your architecture and environment, but if all your key data is on a SAN, it makes sense to replicate there. If your key data is on a NAS, that's likely the best place to replicate. If you're in a mixed environment--or if you want to free yourself from financial ties to your NAS/SAN vendor--standalone is your best bet. The choice between a standalone appliance and a standalone server with software is really a matter of preference. They're basically the same system.

As you're evaluating replication tools, ask detailed questions. Does the tool offer complete copy replication, or does it just transfer changed data? If it is change-based, how much granularity does it offer? If the system transfers changed blocks, and if your changes are generally one or two bytes, it could clog your network. A similar clog could occur if the tool transfers changed bytes, and your enterprise does a high volume of writes to disk.

The growing spectrum of replication tools means users have more choices, and a greater variety of options for architecting the replication process. The key is to know your environment and understand how the different options may fit with what you've got.