A couple of years ago I went to a Juniper marketing event in Sydney. It was a very well run event with lots of good sessions. They talked about JUNOS, virtual chassis, East-West versus North-South network traffic, their ASICs… all good stuff. But the most interesting session was one presented by a client. I always like hearing clients speak at vendor events, provided they bring real world backstory to the table. He spoke about how his company (a bank if I recall correctly) brought Juniper switches into their Cisco dominated networking department. His message was: “You can have a dual vendor networking policy. The sky won’t fall in.” I recalled this after reading Erwins blog post about Cisco vs Brocade and it got me thinking…. could we do the same in Fibre Channel SANs?
Now it’s a well understood requirement: to have a highly available SAN you need dual independent fabrics. Even the smallest customer will normally buy two fibre channel switches and cable them up independently. The only thing that the two fabrics normally have in common is that hosts normally attach to both fabrics and each fabric normally contains often identically configured switches from the same vendor.
It’s common sense. If you have dual fabrics then you get genuine benefits:
- If one switch or fabric fails, traffic routes through the other fabric.
- Human error (like a bad zoning update) can be limited to one fabric.
- Maintenance and upgrades can be done on-line even if they are disruptive to the switch or fabric because traffic can flow through the other fabric.
Examples of fabric names include: Fabric A and Fabric B; Fabric 1 and Fabric 2; the odd fabric and the even fabric; the red and the blue fabric. But how about taking it to a whole new level and having a B and a C fabric. Why B and C? Because one fabric would be exclusively from Brocade the other fabric exclusively from Cisco.
Two suppliers? Could this be good for my company?
Well I could describe at least three separate incidents that I have personally been involved in where firmware errors have occurred in both fabrics at the same time, bringing the customer crashing to their knees. Each one would have been avoided if each fabric had been supplied by a different vendor. In some cases having different firmware levels or different uptimes in each fabric would have also prevented the common event, but this is not always the case. Admittedly the root cause in each case also relates to bugs long since fixed in newer microcode, but the events remain seared into my (and possibly the clients) brain.
So why don’t people do this?
Well for starters:
- Your staff would need skills in two vendors. Sadly some employers hesitate to train their staff on one vendor, let alone two. Of course it will give your staff a wider scope of equipment to work with (which admittedly might make them more employable) and SAN concepts remain the same regardless of vendor.
- The switch sizes and speeds between vendors are not always equal. For example Cisco don’t sell an 80 port switch but Brocade does. Right now Cisco don’t have 16 Gbps FC switches.
- The embedded switches in your blade center chassis would also need to follow the dual vendor policy (presuming this is possible).
- You might hit inter-operability issues where each fabric has conflicting requirements (such as minimum or maximum firmware on FC HBAs), but I doubt this would be a common issue.
- You may pay more. Maybe. But… you might also create competitive pressure and pay less.
- Physically swapping switches between Fabrics would be harder to do. This is true, but how often does this really happen?
To me the main advantage of doing this would be that you are taking your desire for availability to a whole new level. Independent fabrics from different vendors would truly eliminate any risk of common code bugs and make human error harder simply because you could not easily replicate procedural error when working on both fabrics at the same time.
It would be interesting to see a Request for Proposal (RFP) that specifies dual vendors for SAN equipment (though I have never seen this).
Of course, maybe I am just nuts for suggesting this?
How many people are doing this?
Are the results as I described?