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Storing CERN's Search for God (Particles)
Chris Lindquist writes "Think your storage headaches are big? When it goes live in 2008, CERN's ALICE experiment will use 500 optical fiber links to feed particle collision data to hundreds of PCs at a rate of 1GB/second, every second, for a month. 'During this one month, we need a huge disk buffer,' says Pierre Vande Vyvre, CERN's project leader for data acquisition. One might call that an understatement. CIO.com's story has more details about the project and the SAN tasked with catching the flood of data."
Interesting article.
Many years ago when the SSC (Superconducting Super Collider) was still being built in Texas, I went to an HP users group meeting as I was working primarily with HP-3000 systems at the time. The fellow addressing the meeting was the head of the physics department at the SSC. It was a really neat presentation, in which he described a similar, though orders of magnitude smaller data storage requirement, though he was talking terabytes of data per month IIRC. At the time, they were planning on using two arrays of 40 workstation computers to handle the load. This would have been fairly early loosely coupled setup similar to a Beowulf cluster.
After the presentation I went up to him and told him that all I wanted to do is sell him mag-tapes.
These types of experiments evidently produce tons of data. I wonder if the processing could be parcelled out like Stanford's Folding@Home or SETI to speed up data correlations.
This is an ex-parrot!
A standared dual CPU dual core HP server with Windows can keep a 4Gb FC pretty full if set up correctly. I work for a large bank, and we have many a Solaris box that can keep 4 or even 8 2Gb FC cards full into our FC and SATA disk arrays. Not to trivialize the extreme coolness of what they are doing at all, but a PB of data with a few PB of I/O in a day isn't what it used to be. I'm just glad to see they don't use Polyserve, it is worthless for clustering and has caused more downtime at work than it has ever prevented. If they really have that much data they should use 10Gb FC or Infiband. Even our stodgy old bank is implementing our first infiband system so we can move IO at 12Gb instead of the slow 4Gb links.
From my experience, generic blue work clothes (preferably with your name on the breast pocket) work best. I once got into some research facility (they had lasers and everything) because I got out of the elevator on the wrong floor and some guy in a lab coat opened the door for me (I was wearing my work clothes because I was on my lunch break). I wandered about at the place for something like 10 minutes before I found a way out. There was even a security guy of some type sitting at a hallway but he lost interest in me after I looked him in the eye and said hello.
Right now, the average event size for ATLAS is 1.6 MByte and the system is designed to keep around 200 events per second, or roughly 300 MByte. This isn't much of course, but you have to consider that the bunch crossing rate (i.e. the rate at which bunches of protons will collide and generate events) is 40 MHz.
So you have to design a system that boils this rate from 40 MHz down to 200 Hz and only keeps the interesting parts, while also buffering all the data in the meantime. For this reason, the first trigger level is entirely implemented in hardware right in the detector and reduces the rate down to 75 KHz with a latency of 2.5 s. The rest of the trigger works on clusters using Linux computers and has a latency of o(1s).