The PowerMax architecture incorporates an NVMe back end that reduces I/O latency and increases data throughput while maintaining full redundancy. NVMe is an interface that enables host software to communicate with a nonvolatile memory subsystem. The interface is optimized for SSDs and is typically attached as a register-level interface to the PCIe interface.
The NVMe back-end subsystem provides redundant paths to the data that is stored on SSDs. This redundancy provides seamless access to information even if a component fails or is being replaced.
Each PowerMax disk array enclosure (DAE) can hold twenty-four 2.5-inch NVMe SSDs. The DAE also houses redundant canister modules (link control cards, or LCCs) and redundant AC/DC power supplies with integrated cooling fans.
The back-end directors are connected to each DAE through a pair of redundant back-end I/O modules. The back-end I/O modules connect to the DAEs at redundant LCCs. Each connection between a back-end I/O module and an LCC uses a completely independent cable assembly. Within the DAE, each NVMe drive has two ports, each of which connects to one of the redundant LCCs. PowerMax systems use an active/active RAID group accessing scheme called Smart RAID. As shown in the following figure, this scheme enables RAID groups to be shared across directors, giving each director active access to all drives on the brick or zBrick.
Figure 3. PowerMax Smart RAID for dual-ported drive access
The dual-initiator feature ensures continuous availability of data in the unlikely event of a drive-management hardware failure. Both directors within an engine connect to the same drives through redundant paths. If the sophisticated fencing mechanisms of PowerMaxOS detect a failure of the back-end director, the system can process reads and writes to the drives from the other director within the engine without interruption.
The following figure summarizes the benefits of NVMe on the PowerMax system and the benefits that are realized by the application: