Cisco MDS, NVMe, and Flexibility

Disclaimer: I recently attended Storage Field Day 20.  My flights, accommodation and other expenses were paid for by Tech Field Day. There is no requirement for me to blog about any of the content presented and I am not compensated in any way for my time at the event.  Some materials presented were discussed under NDA and don’t form part of my blog posts, but could influence future discussions.

Cisco recently presented at Storage Field Day 20. You can see videos of the presentation here, and download my rough notes from here.


NVMe, Yeah You Know Me

Non-Volatile Memory Express, known more commonly as NVMe, is a protocol designed for high performance SSD storage access.  In the olden days, we used to associate fibre channel and iSCSI networking options with high performance block storage. Okay, maybe not the 1Gbps iSCSI stuff, but you know what I mean. Time has passed, and the storage networking landscape has changed significantly with the introduction of All-Flash and NVMe. But NVMe’s adoption hasn’t been all smooth sailing. There have been plenty of vendors willing to put drives in storage arrays that support NVMe while doing some translation on the backend that negated the real benefits of NVMe. And, like many new technologies, it’s been a gradual process to get end-to-end NVMe in place, because enterprises, and the vendors that sell to them, only move so fast. Some vendors support NVMe, but only over FC. Others have adopted the protocol to run over RoCEv2. There’s also NVMe-TCP, in case you weren’t confused enough about what you could use. I’m doing a poor job of explaining this, so you should really just head over to Dr J Metz’s article on NVMe for beginners at SNIA.


Cisco Are Ready For Anything

As you’ve hopefully started to realise, you’ll see a whole bunch of NVMe implementations available in storage fabrics, along with a large number of enterprises continuing to have conversations about and deploy new storage equipment that uses traditional block fabrics, such as iSCSI or FC or, perish the thought, FCoE. The cool thing about Cisco MDS is that it supports all this crazy and more. If you’re running the latest and greatest NVMe end to end implementation and have some old block-only 8Gbps FC box sitting in the corner they can likely help you with connectivity. The diagram below hopefully demonstrates that point.

[image courtesy of Cisco]


Thoughts and Further Reading

Very early in my storage career, I attended a session on MDS at Cisco Networkers Live (when they still ran those types of events in Brisbane). Being fairly new to storage, and running a smallish network of one FC4700 and 8 Unix hosts, I’d tended to focus more on the storage part of the equation rather than the network part of the SAN. Cisco was still relatively new to the storage world at that stage, and it felt a lot like it had adopted a very network-centric view of the storage world. I was a little confused why all the talk was about backplanes and port density, as I was more interested about the optimal RAID configuration for mail server volumes and how I should protect the data being stored on this somewhat sensitive piece of storage. As time went on, I was invariably exposed to larger and larger environments where decisions around core and edge storage networking devices started to become more and more critical to getting optimal performance out of the environment. A lot of the information I was exposed to in that early MDS session started to make more sense (particularly as I was tasked with deploying larger and larger MDS-based fabrics).

Things have obviously changed quite a bit since those heady days of a network upstart making waves in the storage world. We’ve seen increases in network speeds become more and more common in the data centre, and we’re no longer struggling to get as many IOPS as we can out of 5400 RPM PATA drives with an interposer and some slightly weird firmware. What has become apparent, I think, is the importance of the fabric when it comes to getting access to storage resources in a timely fashion, and with the required performance. As enterprises scale up and out, and more and more hosts and applications connect to centralised storage resources, it doesn’t matter how fast those storage resources are if there’s latency in the fabric.

The SAN still has a place in the enterprise, despite was the DAS huggers will tell you, and you can get some great performance out of your SAN if you architect it appropriately. Cisco certainly seems to have an option for pretty much everything when it comes to storage (and network) fabrics. It also has a great story when it comes to fabric visibility, and the scale and performance at the top end of its MDS range is pretty impressive. In my mind, though, the key really is the variety of options available when build a storage network. It’s something that shouldn’t be underestimated given the plethora of options available in the market.