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DiFX activities at MPIfR
...including the upgrade of the MPIfR correlation cluster

Helge Rottmann (MPIfR)

9th DiFX Workshop 16-20 November 2015 Hobart, Australia


Good news frst...
....DiFX is running fne




No serious issues in 2015 Correlation is running uninterrupted (with occasional Mark5 hickups) Implementation of new features is progressing (e.g. Mark6) Working collaboration / good support

=> Everybody (at MPIfR) is very happy

....even the geodesists!


MPIfR activities - GMVA


Global mm-VLBI Array (GMVA) is doing VLBI at 3mm and 7mm wavelengths Coordinated & correlated by the MPIfR Typically two observation sessions per year

Phased-ALMA will possibly join GMVA observations starting in cycle-4 ( >2017)


MPIfR activities - GMVA




Requirement by ALMA: demonstrate that GMVA + ALMA observations can be succesfully correlated Test observations: ALMA + VLBA + Effelsberg in August 2015 Correlation at MPIfR succesful


MPIfR activities - EHT




Event Horizon Telescope (EHT) is doing VLBI at 1mm wavelength Recent upgrade to broadband mode: 2 GHz / dual-pol => 16 Gbps recording rate (Mark6) Next upgrade in 2016 to 32 Gbps Final goal in recording rate: 64 Gbps 50/50 correlation split between MPIfR & Haystack

Phased-ALMA will possibly join 1mm observations starting in cycle-4 ( >2017)


MPIfR activities - EHT


Test observations between ALMA and EHT in March 2015 Correlation done at Haystack using DiFX Fringes between ALMA and Pico Veleta!


Geodetic activities - VGOS


Bonn correlator is used approx. 50% for correlation of geodetic experiments (IVS) VGOS = VLBI2010 Global Observing System


next-generation geodetic experiments High-bandwidth recording (currently 16 Gb/s) High-duty cycle (envisioned: 24x7)



Demonstration (2015) that VGOS data can be correlated successfully with DiFX


Mark6 support
Currently 4 Mark6 units 2x full unit (4 banks) 2x half unit (2 banks)



Native playback mode implemented by Walter Brisken Operational tools (mk5daemon etc.) work in progress Tests so far look promising Possible issue with playback speed (reported also by Haystack & JIVE)


Now...cluster renewal
Existing cluster


Purchased in 2008/2009 Slowly falls apart Not suited anymore for broadband correlation

Compute nodes: 60 x dual quadcore = 480 cores Storage: 14 RAID servers = 614 TB Interconnect: DDR Infiniband (16 Gbps) 2 x 1 Gbps Ethernet CPU: Intel (Harpertown) Performance: 5 Tflops (Linpack)


Existing cluster will go out of commission

First week of december 2015


New cluster specs
Compute nodes:
64 x Haswell E5-2660v3 (2x10 Cores, 2.6 Ghz)

Head Node:
24 disk SAS RAID (fast IO) Haswell E5-2667v3 (2x8 Cores, 3.2 GHz) Secondary head node (parallel correlation) from old cluster

Storage:
2 oldest storage servers will be replaced SAS RAID (36 x 4TB disks)

Cluster interconnect:
FDR Infnband (56 Gbps)

Cluster benchmark
53 Tfops (Rpeak) 43,8 Tfops (Rmax)