Managing RAID on Linux

Controller Memory

The controller uses memory to cache data during write operations. This process improves overall write performance and helps the system recover from a crash by storing unwritten data in the controller cache and committing the data to disk when the system restarts. The more controller cache you have, the more data the card can buffer before committing the data to disk.

All RAID controllers come with a fixed amount of onboard memory, but it can usually be augmented by purchasing memory expansion kits.

Tip

In some cases, memory expansion kits are available only at the time of purchase. You may not be able to order the kits standalone and install them yourself. While many RAID controllers use standard 72-pin SDRAM DIMMs (Dual Inline Memory Modules), purchasing untested third-party upgrades is likely to void the controller’s warranty. Please check with the vendor before upgrading any controller.

Purchasing additional controller memory is a good idea if you typically work with a lot of large files, such as audio, video, or image files. If you have a lot of small files or files of varying sizes, additional cache memory is unlikely to improve performance. In general, additional controller cache memory will improve performance on systems that have a lot of large sequential file I/O. Systems that lean toward random I/O on small files won’t see much of a difference. A typical office file server probably doesn’t need extra memory. A graphics or video production workstation does. ...