Battery backup write cache for controllers - should it be disabled?

You might be aware that now a days many high-end and high-spec disk subsystems provide high-speed cache facilities to reduce the latency of read and write operations. In general this cache is supported by a battery-power backup facility, which is necessary to maintain the data in cache in case of any power surge in hardware. But the implementation of this method varies from manufacturer to manufacturer. Microsoft recommends to switch off (disable) this feature for write cache, for 100% reads method this cache can be enabled and in any case you must test the implications.

Recent changes with disk controller and storage manufacturers enhanced the pending writes in the cache that are treated as if the failure or restart never occurred. Most manufacturers' implementations immediately flush pending writes to physical disk during the restart operations. I'm not vouching any specific storage manufacturer here, but giving a general guidance on what you must choose within your environment as it varies.

For further information on using this type of controllers refer to KBAs 234656 & Q86903 links. In addition to this  you should make sure that your disk controller has features such as safeguards to avoid uncontrolled reset of the caching controller, on-board battery backup, and mirrored or error checking and correcting memory.

As usual the suggestion is to check with the hardware vendor to ensure that the write cache includes these and any other features necessary to avoid data loss.Also it is a best practice to place the transaction log file on a disk with the RAID controller, where on this array should have a (battery-backed) write-back cache to speed log writes.