Home > Uncategorized > A Rant about Ethernet Based Storage Networks

A Rant about Ethernet Based Storage Networks


There have been some really interesting discussions within the NetApp technical community around the benefits of NFS vs Fibre Channel for Oracle and VMware workloads, much of which I’m planning on plagiarizing and passing off as my own work on this blog, but in the interests of trying to keep the small shreds of integrity I have left intact, I thought I’d post up my contribution to the conversation  first, because a friend of mine suggested the issues raised in the rant would make a good blog post

This response came after a series of posts on whether you needed to put in a dedicated ethernet network to carry the storage traffic, which would tend to diminish  much of the “Ethernet Infrastructure is Cheaper” argument,  or whether you can simply carve out a VLAN instead, what we considered to be best practice, and whether that matches what happens in a FlexPod.

My Response (slightly edited where you see the [ …]  but still including the rant meta-tags that I feel should be made an official part of HTML 6) follows

<rant>

[You can just use] a VLAN, but you’d want to make sure the underlying Ethernet network was designed with storage style SLO’s eg. Not oversubscribed, no single points of failure, non-disruptively upgradable, port channels set up correctly, Jumbo frames set up correctly etc.

Using Ethernet networks designed for typical “user LAN” SLO’s and expectations for a storage network will probably screw up something at some time and is IMHO the reason why iSCSI and NFS still gets a bad reputation.

There are a number of people out there in customer network teams [….]  that think they know how to design a reliable high performance Ethernet network with storage level SLO’s and many of those people overestimate their capabilities. For that reason storage teams have rightfully been wary of the network team and use FC infrastructure as an excuse to keep them from fiddling about in stuff they don’t really understand. Ethernet based storage networks make that much harder to do, but running up a brand new network design/implementation specifically for storage is still a reasonably good idea unless there is a good reason to believe the existing network has been designed with storage class SLOs in mind.

That is partly the reason why in a FlexPod, the only thing you don’t flex is the network configuration. In a FlexPod you can safely carve out a VLAN, apply the appropriate COS to it (as specified in the design guide) and be confident that you’re going to get a good result, there’s almost 40Gbit of bandwidth available in the current design, so it’s pretty unlikely you’re going to run out of that resource in a hurry, and if you do … buy another FlexPod.

Personally I’m a strong believer in multi-purpose Ethernet based networks based on 10Gbit/40Gbit with storage class SLO’s. The economic benefits go way beyond just reducing the costs of FC infrastructure and goes to the principal of large pools of [stateless] physical resources  [from which virtual constructs are]  provisioned automagically on demand, and this ties in really nicely with [NetApp’s] overall value proposition. Cisco, not surprisingly have a pretty good pitch around this, and [it would be worth working with them on this]. Furthermore, it also allows you to get involved in the ever increasingly sexy subject of software defined networking.

Transformation of the network infrastructure gets LOTS of attention at the C-Level and providing solid justifications / use cases for that can help [the customer accelerate their justifications for a datacenter transformation projects].

Because of that I would never be shy about pushing NFS (or going forward SMB3) on Ethernet as a superior solution to FC, especially with things like RoCEE on the horizon as it might just be the thing that disrupt [legacy methods] as it has done in some of NetApp’s largest accounts many times over.

For me supporting FC (or even iSCSI)  is more about helping a customer to protect the investment they’ve already made in legacy infrastructure while they migrate to something more efficient and flexible.

Finally this is less about NFS vs FC than it is about FlexVols vs LUNS, and LUNs are really DUMB storage containers … don’t encourage people to keep using them when they have a better alternative

</rant>

I’d be interested on any perspectives or particular interests, because I’m digging through some of our internal and customer facing documents to summarise exactly what the benefits are, where the limits are, and what you need to do to implement an ethernet network with storage class SLOs at small and large scales.

Regards

John Martin

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