The Mark 5B VLBI Data System Alan Whitney MIT Haystack Observatory 10 Jan 2006 IVS General Meeting Concepion, Chile

Mark 5A Data Acquisition System (introduced 2002)

Main features of Mark 5A Data System Direct plug-compatible replacement for 64-track Mark4 or VLBA tape drives Record/Playback at rates up to 1024 Mbps Two independent ‘8-pack’ disk modules can be used in ‘ping-pong’ fashion for nearly continuous recording Will record 8, 16, 32 or 64 tracks from Mark4 formatter (1024 Mbps max) or VLBA formatter (512 Mbps max)

Current Mark 5A Status ~120 Mark 5 systems deployed; >90% of tape systems have been replaced >1000 Mark 5A ‘8-pack’ disk modules deployed (>2 PB of storage!); growing rapidly! Many stations are now entirely Mark 5A, except in some cases for data which goes to VLBA correlator 1 Gbps experiments are now routine for both geodesy and astronomy VLBA is converting to Mark 5; all VLBA stations have Mark 5A, but correlator not yet fully outfitted

Mark 5B Data System Features Full VSI-H compatibility Same chassis as Mark 5A; uses same disk modules; requires Mark 5B I/O card 1024 Mbps record/playback Eliminates need for external formatters, but requires sampler adapter for Mark 4/VLBA DASs to provide VSI-compatible output Station Unit capabilities for connection to Mark 4 correlators is designed into Mark 5B Extensive built-in phase-cal extraction and state counting on both data record and data playback Front-panel status display – 8 tri-color LEDs DIM and DOM capabilities are separate FPGA downloads FPGA is programmable via software Development support from Mark 5 development consortium – BKG, EVN, KVN, JPL, MPI, NASA, NRAO, USNO

VSI-H VSI-S VSI-E

Mark 5A/B System Comparisons Mk5AMk5B Data Interface Emulates Mk4/VLBA tape transport VSI-H (32MHz max clock rate) Max data rate 1024 Mbps Record modes 8, 16, 32, 64 “tracks” 1,2,4,8,16,32 bitstreams Disks Mk5 “8-pack”Same Chassis Mk5Same I/O card Mk5AMk5B SS card XF2 I/O-SS intf Modified FPDPFPDP

Mark 5B Functional Block Diagram

Mark 4 Station Unit emulation Mark 4 Station Unit

Mark 5B I/O Board FPDPVSI OutputVSI Cntl/Mntr VSI Input 256MB memory PCI Connector

Mark 5B Status Checkout of Mark 5B hardware is complete Successful correlation and fringes from Mark 5B data (software-converted to Mark 5A format and correlated on Mark 4 correlator) Direct connection to Mark 4 correlator is coming along well Mark 5B support software is functional but needs some additional capability and testing before release 15 Mark 5B I/O boards have been built and tested – will be distributed to Mark 5 development consortia members in near future Design is being transferred to Conduant Corp for replication and sale – expect Mark 5B to be orderable ~early Spring 2006

Reasons to adopt Mark 5B Eliminate need for expensive external formatters; particularly important for new stations or stations without existing Mark 4 or VLBA formatters With a 14-BBC Mark4 or VLBA4 system, up to 1792 Mbps can be recorded with two parallel Mark 5B systems; current 14-BBC systems can only generate a maximum of 1024 Mbps of formatted data Extensive phase-cal extraction and state counting capabilities for better diagnostics and better system calibration Replace unreliable Station Units on Mark 4 correlators; SU capability is built into Mark 5B

Mark 5A/B Compatibility Mark 5B can play only Mark 5B recordings (VSI format in/out) Upgraded Mark 5A (“Mark 5A+”) will be able to play: -All Mark 5A recordings -Mark 5B recordings made in selected modes; playback will be VLBA-track-format Mark 5A+ design is now just starting and will take several months to complete Bottom line: Existing Mark 4 correlators with only Mark 5A units will be able to process data from both Mark 5A and Mark 5B units during transition period to Mark 5B.

Mark 5B+ (2048Mbps) Conduant has introduced an upgraded StreamStor (dubbed “Amazon”) that supports up to ~3 Gbps an FPDP2 interface which allows clocking at 64 MHz Mark 5B I/O card has been designed to support input VSI-H clock rate of 64MHz, as well as FPDP2 compatibility, to support max recording rate of 2048 Mbps Testing with prototype SATA Amazon board at Haystack was successful; PATA version compatible with Mark 5 is under development by Conduant May be desirable to record across 2 disk modules (16 disks) simultaneously Playback is limited to 1024 Mbps Much software work and testing remains to be done No promises yet on date of general availability

Mark 5A/B/B+ System Comparisons Mk5AMk5BMk5B+ Data Interface Emulates Mk4/VLBA tape transport VSI-H (32MHz max clock rate) VSI-H (64MHz max clock rate) Max data rate 1024 Mbps 2048 Mbps Record modes 8, 16, 32, 64 “tracks” 1,2,4,8,16,32 bitstreams Same as Mk5B Disks Mk5 “8-pack”Same Chassis Mk5Same I/O card Mk5AMk5B SS card XF2 Amazon I/O-SS intf Modified FPDPFPDPFPDP2 (clocks on both edges

Mark 5 Upgrade Costs Target Existing Mk5AMk5BMk5B+ 0$16.3K~$18-20K~$20-22K Mk5A-~$2-2.5K (Mk5B I/O) ~$ K (Mk5B I/O plus Amazon) Mk5B--~$9555 (Amazon) Note: Does not include external cabling costs, typically a few hundred dollars

Disk-Media Status Hard disk price vs capacity/performance continues to drop -Now at or below ~$0.50/GB and continues to drop (Mark 4/VLBA tape is ~$2.00/GB) 250 GB disks now common – 8-pack of 250GB disks comparable to ~7 VLBA/Mark 4 tapes 400 GB disks are available – 8-pack of 400GB disks comparable to ~11 VLBA/Mark 4 tapes 700 GB disks expected by end 2005 – 8-pack of 700GB disks comparable to ~19 VLBA/Mark 4 tapes; ~24 1 Gbps unattended!

Tape vs. Disc Price Comparison

Disk-Media Reliability Based on statistics collected at Haystack, average disk drive failure rate is ~0.5% per year Failure rate of Hitachi 250GB has been higher than average Conduant has qualified drives from Maxtor, WD and Seagate 400GB – Seagate 250GB – Western Digital RAID Edition (high-reliability) 250GB – Maxtor Maxline III (high-reliability) Conduant is shipping these disks in assembled Mark 5 disk modules Disk reliability at high altitudes is under investigation

Summary Mark 5B is nearly ready for prime time Upgrading to Mark 5B may be particularly advantageous in certain situations Mark 5B+ (2 Gbps) is on the horizon Expect continuing upgrades to Mark 5 over the next few years

Plans for Serial-ATA Support PATA and SATA disk modules will be interchangeable in Mark 5 systems Biggest challenge was finding module SATA connectors with durability Requires upgrade kit for current Mark 5 systems - new chassis backplane with separate connectors for PATA and SATA New SATA disk modules have been designed SATA module should be able to support 2048 Mbps in near future with Mark 5B and NG StreamStor board SATA module price will be about same as current module Expect SATA modules to be available late 2005

Mark 5B Interface Boards VSI-4 sampler adapter board Will be placed inside Mark 4 formatter to upgrade to VSI Uses existing Mark 4 samplers and 1pps generator 2 VSI output connecters at 1024Mbps each (though data rate is restricted to 1792 Mbps by 14 BBC’s) Prototype boards ready for checkout VSI-C sampler adapter Interfaces VLBA samplers to VSI Designed at Metsahovi Correlator Interface Board (CIB) Interface between Mark 5B and Mark 4 correlator PCB currently in fabrication Upgraded Serial Link boards for Mark 4 correlator Designed at MPI Prototypes have been tested; replication to begin soon

VLBI Standard Interface (VSI) Joint effort by astronomy (GVWG) and geodetic (IVS) communities The purpose of VSI is to define a standard interface to and from a VLBI Data Transmission System (DTS) that allows heterogeneous DTS’s to be interfaced to both data-acquisition and correlator systems with a minimum of effort Focuses on those functions independent of DTS technology VSI-H – complete (Aug 2000) Data and control interfaces for recording and playback, including connectors and pinouts Electrical and timing specs Won national award in Japan in 2001! VSI-S – complete (Feb 2003) Communications model Application Protocols Command/Response Syntax Suggested base command set VSI-E (e-VLBI) – draft specification and reference implementation available VSI specs available at VSI is now widely accepted worldwide with a substantial number of VSI-H compliant components available