ZMCP 3.0 (Zero-Maintenance Cache Protection) is a unique new take on protecting data stored in the volatile cache of the controller during a power outage. This approach allows RAID controllers to function with write back caching without endangering data. Write back caching provides the maximum performance for connected drives. Li-Ion (Lithium Ion) batteries have several disadvantages, and the AFM-700 ZMCP solution from Adaptec looks to change the utilization of cache protection systems.
The black container that forms the 'battery' of the solution is actually a super capacitor connected to a PCB containing 4GB of SLC NAND flash. In the event of a power failure, the super capacitor will provide enough power for the controller to flush the contents of the DRAM to the attached SLC NAND. SLC is employed due to its endurance, resistance to heat and very fast write access time.
A benefit of using non-volatile NAND to store the flushed data is that when data is committed to the NAND, it can be stored for years without power. SLC typically has data retention of 10 years without power. Upon power restoration, the data is copied back from the NAND to the array and the adapter functions as normal. Li-Ion solutions merely keep the DRAM onboard the controller alive with power, preserving the data in the volatile DRAM until the battery discharges entirely, usually within 72 hours.
Li-Ion batteries also require hours to charge when installed, and this leads to compromised performance due to adapters switching out of write back mode until the battery is charged. Another unfortunate characteristic of Li-Ion batteries is that they require discharging to determine the life expectancy of the battery. The performance of the adapter is compromised during this cycle. While discharging and recharging the adapter switches back to write thru mode.
The AFM-700 super capacitor takes a few minutes to charge during boot up, and then does not require powering down for monitoring. The super capacitor is monitored from the MaxView Storage Manager without disrupting operations or impacting performance. The AFM-700 also reports its temperature, allowing administrators to monitor the server temperature remotely.
With a longer lifespan (five years at 50C) and more durability in high heat scenarios than Li-Ion solutions, the AFM-700 modules will cut OpEX and TCO requirements significantly.
maxCache 3.0 provides users with a means of caching HDD pools with faster SSDs, expanding the performance of the underlying array exponentially. This latest version of maxCache supports both read and write caching. Adaptec has also expanded maxCache to introduce protection from SSD failure via redundancy with RAID 1E and RAID 5.
The new ODU (Optimized Disk Usage) approach of forming a cache pool allows for more flexibility when configuring the attached flash. This approach will help to maximize the investment in flash-based devices by also allowing the pool to have usable volumes, or even boot volumes. This could also allow for interesting tiering configurations with third party applications.