Why is persistent cache important?

Leah Schoeb, partner with Evaluator Group, discusses the importance of persistent cache in this Expert Answer.

What is persistent cache and why is it important?

Some call non-volatile memory or a solid-state storage tier "persistent cache" to distinguish it from cache memory.

Persistent cache is counted and considered actual storage capacity and cache isn't. A cache is considered temporary, so in the case of a system reboot or crash, the data held in a cache is gone. Vendors back up the data on a cache with a battery, usually called battery backup, in order to help a system come back in a healthy state. But if the battery is not on or loses power, the data is lost. Also, some vendors may go a step further and flush data to battery-backed DRAM as additional protection against data loss, just like what you would find on a controller card or storage controller when data is flushed to battery-backed cache in case of failure.

Persistent cache means information is stored in "permanent" memory, so data is not lost after a system restart or system crash as it would be if it was stored in cache memory. This is very important if you plan to use flash memory as a storage tier and need that data to be stored with data protection and enterprise data services.

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