One of our clients asked us how we handle latency, and not just a few ms across racks but 2 and even 3 digit ms latency that indicates geographically separate locations across continents, not just a country. Not only that, the “pipes” involved are 10Gbps and we had to fill them. We have the theories and made models of how it would work. We perhaps might not be able to fill a 10Gbps fully with one stream, we could fill it with multiple streams but we had to validate this conclusion.
The question now becomes, how do we test this. We’ve done our research and there are only a few commercial solutions available like the Netropy 10G2 which is a 4 port, 2 lane hardware latency simulator for $30,000 new. Not only is that outside my budget, it is still limited to simulating 2 10Gbps pipes while we need at least 3 lanes (6 ports) and possibility to expand to more as necessary. We decided it was cheaper in terms of total cost to put the research into creating our own Latency Simulator.
We recently got sent a Dell R620 to evaluate and while its technical specification is amazing there are a few things that need to be handled first.
As far as Ubuntu and the Dell R620 go, Precise (12.04) is the only way to go here. Every release before Precise has issues with this hardware in one way or another. This is new hardware of after all.
For our “use case” we downgraded the PERC H710P controller to a H310 controller so we can have direct access to the drives via pass-through. The H310 allows TRIM support for SSDs and SMART data via smartctl to be used without any problems. If you are interested in SMART information and PERC H700 series RAID controller, I posted about possible workarounds at Dell’s customer support site.
Doing subnet calculations by hand can be tedious and thankfully there are tools available online to help with that. One in particular Subnet Calculator with a PHP backend was handy and compact.
It is not unusual for me to find 10,000 Euro worth of networking equipment on my desk one day. It usually means that I have a long week of reading and testing ahead of me as I am the only person in the company, let alone building, that has ever seen or worked with these devices before. That means I am on my own aside from an Internet connection.
While your mileage may very, I’ve had the joy (and horror) of testing these devices as ‘drop in replacements’ to the test environment that we are using. In some instances, things just worked out of the box, however there are a few devices that needed to be poked a few times to get things moving.
Sometimes you get a web-hosting environment that only serves non-ssl (http) content. If you need to do any type of management through tools like phpMyAdmin, then you can see the problem with this. All it would take is someone on your network or on the Internet to sniff the traffic and retrieve your username and password, then they too can do a bit of “management” on your site.
If you also have secure shell (SSH) access, then there is a way to manage your site securely by using SSH’s venerable port forwarding (SOCKS). The trick is to tell your management tools to only listen or respond to connections coming in over SSH instead of normal traffic.