EMC VNX: New OS + PCIe Gen 3 = a flash array turning point

EMC’s refresh of its VNX line of unified storage arrays is largely based on an almost complete re-write of its near 20-year-old Flare operating system. Flare was on its 32nd release and has been replaced with a new OS, MCx, but what exactly has changed under the bonnet?

In short, MCx has been developed to take advantage of Intel multi-core processors where Flare was completely unable to do so. In addition VNX controllers also now use the latest Gen 3 PCIe cards and so physical bandwidth is also hugely increased.

All this amounts to unified storage arrays with much-boosted capabilities when it comes to exploiting the speed of flash storage.

Flare was originally developed by Data General (acquired by EMC in 1999) for the Clariion brand of arrays, and like storage operating systems from all vendors way back when, was written for single-core processors.

When multi-core processors arrived Flare was rewritten to allocate different functions – eg, RAID, memory, data placement, data services – to different cores, but with one function assigned to one core it was easy to max out.

But at the time with spinning disk the norm there was no great need to overcome this bottleneck. That all changed with flash storage, however.

Flare as-was, simply couldn’t support the I/O and latency requirements of flash and this was where EMC fell behind the flash startups that built systems from the ground up.

So, MCx was rewritten for multi-core processors – the new generation of VNX uses Intel Xeon 5600 CPUs – and all processing functions are parallelised across the 32 cores and EMC claims something like 40,000 IOPS per core and into the hundreds of thousands per controller up to 1m IOPS in the VNX 8000 with latency staying below 2 microseconds.

Another key advance is the use of Gen 3 PCIe cards.

While the processors could be a bottleneck in legacy arrays so could connectivity in and out of the array via PCIe. Gen 3 boosts bandwidth and lane count between the processor and the storage as well as front (Fibre Channel, Ethernet) and back end (SAS) port bandwidth.

All of which helps put the new VNXs in a similar performance ballpark to the all-flash vendors. According to EMC mid-tier business director, Sean Horne, that means customers can now buy a midrange VNX array and look at having enough headroom for four or five years of growth in virtual machine count and performance requirements.

What EMC is hoping is that customers who have been, rightly, impressed with the performance of flash arrays from the startups will now be able to get similar performance for their virtual environments from EMC.

It certainly puts EMC at the forefront of the big six storage vendors; re-engineering an existing array family for flash, rather than throw flash at legacy OS and controller hardware. And for that reason it is a turning point in the flash storage story.

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