What is persistent cache and why is it important?
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.
Dig Deeper on Solid-state storage
Related Q&A from Leah Schoeb
Leah Schoeb of Evaluator Group discusses DIMM-connected flash as compared with PCIe flash benefits in this Expert Answer. Continue Reading
Leah Schoeb of Evaluator Group discusses the variety of enterprise SSD options available today in this Expert Answer. Continue Reading
Leah Schoeb of Evaluator Group discusses whether the emerging SCSI Express and NVMe standards will have an impact on PCIe flash adoption. Continue Reading