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Subject: Promising PCEVN/eVLBI developments at Metsahovi
From: Jouko Ritakari <[log in to unmask]>
Reply-To:European VLBI Network discussion.
Date:Mon, 14 Jun 2004 10:06:59 +0300

TEXT/PLAIN (50 lines)


One week ago we finally received the first nVidia nForce3 250 GB-based
motherboards and got very promising initial test results. These
motherboards are the first ones that have a gigabit Ethernet controller
integrated in the motherboard chipset (and have any real chance of
succeeding in high-speed eVLBI, the old architectures just are not fast

The nForce3 250 GB chipset also gives more flexibility in using IDE disks
since it supports simultaneously 4x old PATA and 2x new SATA disks, six
disks in total per PC.  Migration to all-SATA will be easy since the next
variant of nForce3 chipset will have native support for 2x PATA and
4x SATA disks.

The first tests were record and playback tests between the VSI port and
the hard disks. We tested both directions at 640 Mbit/s speed without any
problems, which indicates robust operation in 512 Mbit/s experiments.

In the second test we used two old nForce2 chipset based computers to ftp
data from one of the new computers. In this test the aggregate bandwith
was 800 Mbit/s, twice the speed anybody has managed to reach in earlier
disk-to-net-to-disk or DAS-to-net-to-correlator eVLBI tests.

In the third test we ftp-transferred files between two nForce3 based
computers and got 640 Mbit/s speed in disk-to-ethernet-to-disk transfers.
We suspect that in this test the limiting factor was the disk transfer
speed, we were using the inner tracks of three ancient (two years old)
120GB disks.

All these tests were done with standard Linux without any parameter tuning,
jumbo frames or other things that could further improve the speed.

Obviously the next step would be an international data transfer test
(using one of the new reliable UDP-based protocols) followed by an
international eVLBI test.

If any of you are willing to collaborate, please let us know.

Best regards,

Jouko Ritakari and Ari Mujunen
Metsähovi Radio Observatory

For those that are interested, we used the following equipment:
VSI data acquisition/playback: VSIB and VSIC boards designed at Metsähovi.
Motherboard: EPoX 8KDA3J (nForce3 250 GB chipset), price 112.90 euros.
Processor: AMD Athlon 64 3200+, price 297,90 euros.
Memory: Two 256MB DDR 400MHz PC-3200 modules, price 89.80 euros.

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