CGTalk - Network speed test

mrben

11-27-2007, 03:30 PM

Hello,

A while back I posted and had a lot of advice about upgrading our network from a very shaky 1Ge network to a much faster network with Aftereffects machines connected to their storage via 10Ge.

Obviously playback in Aftereffects is about workstation speed and RAM not network speed, however our network currently max's out a lot when you have a few compositors working at once in HD.

We're still unsure whether a 10Ge network and decent server is over specced for Aftereffects as there's always an upper limit depending on processor speed rather than the network's ability to deliver frames to the workstations on time.

We're putting the final touches to our plan but I was wondering if anyone knows of any a way to measure a network's ability to deliver frames to the desktop ?

cheers
ben

beenyweenies

11-27-2007, 11:39 PM

I'm no network expert so take my feedback with a grain of salt, although I am in the process of gearing up my studio along a similar line and have done quite a bit of research.

- Gbe - Gigabit tends to have more data spikes than other transport mediums (like Fibre) so you need to account some overhead, maybe 25%, to allow for this. You should also expect to lose about 25% of the "rated" speed since Gbe rarely actually hits 100MBps even in controlled test environments. I'm sure 10Gbe is no different since it's still TCP/IP-based.

- To determine bandwidth needs in our network, I have been approaching it like this. The highest datarate file you might need, plus overhead/rated speed loss, multiplied by number of streams per user, multiplied by number of users. If you are using uncompressed HD (about 120MBps datarate) and each user on average needs to use 5 layers of video and you have 4 users running all at once, that adds up to 3 gigabytes per second of data needed, or 35Gbps+. This of course is impossible since there is no RAID system that can serve up data that fast. Obviously uncompressed HD is out, but even using uncompressed SD video (datarate around 27MBps) results in a bandwidth need of around 8Gbps using the stats above.

Because of this, You can probably get away with it if your HD projects can use proxies (say, DVCPROHD) for any footage, and users have local drives dedicated to cache, etc. Even better if you have fewer users or fewer streams per user needed.
In my studio we are building out what will be closer to 4Gbe, but we mostly do editing (low bandwidth needs with proxies) and motion graphics (low bandwidth needs as well), not so much compositing with video footage. What compositing we do is with DVCPRO 50 or DVCPROHD so I think we'll be ok.

Anyway, I have been increasingly interested in the networking side of this game, so please share any results you have when you guys get this rolling, including any setup issues if you encounter them.

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