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XCube Data System: Next-Generation VLBI Data Solution

The XCube Data System, developed by a company in Nashua, NH, is a real-time high-data-rate disk-array system for VLBI applications. It offers sustained recording rates of 8 Gbps and supports inexpensive commodity SATA disks. This system is currently under evaluation at Haystack Observatory for its potential use in VLBI projects.

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XCube Data System: Next-Generation VLBI Data Solution

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  1. Potential VLBI2010 Data System Alan WhitneyMIT Haystack Observatory Mikael Taveniku XCube Systems 24 Feb 2011 East Coast VLBI meeting Haystack Observatory

  2. XCube data system (candidate for next-generation VLBI data system) • System developed by small company in Nashua, NH for automobile industry • Real-time high-data-rate disk-array data system based on fully COTS hardware • 8 Gbps sustained recording rate from RDBE demonstrated • First COTS-hardware system that (to my knowledge) properly handles slow and/or failed disks for VLBI application • Runs on Linux platform with some modified kernel code and drivers for efficient memory management • Hardware/software combination is highly tuned for performance • System currently under evaluation at Haystack

  3. Characteristics • Two 10GigE data interfaces • 8Gbps sustained to 16 SATA disks • Supports inexpensive commodity SATA disks (but disks must be qualified) • eSATA cable connections from controller to disk module(s) [four disks per cable]; cable ordering does not matter • Records to standard Linux files • Can use XCube disk modules (similar to Mark 5 modules) or existing Mark 5 modules modified with new module backplane and front panel (with e-SATA and power connectors) • Playback as standard Linux files • Appears to be potentially good fit to two current VLBI projects: • VLBI2010 – currently planning 16Gbps/stn, possibly expanding to 32Gbps/stn • mm-VLBI – currently planning 16Gbps/stn, expanding to 64Gbps/stn over next few years

  4. Demonstrations • Haystack: Dec 2010 • Recorded two 10GigE data streams at 4Gbps each (from RDBE) to 20 disks • One 4-disk eSATA cable was disconnected from a module while recording; system transferred load to remaining 16 disks within <1 second • Socorro: Jan 2011 • Simultaneously recorded identical 2Gbps data stream from RDBE to both Mark 5C and XCube systems; no problems • Cross-correlated Mark 5C vs XCube data • With exception of minor bookkeeping hiccup, cross-correlation worked perfectly on first try

  5. Work in Progress • Minor software revisions being made to support several VLBI-specific issues: • VSN support • Gather individual disk-performance statistics • Allow one disk module to record/playback undisturbed while utility operations are peformed on another (mount/dismount, read VSN, etc) • Write VSI-S wrapper for VLBI control/monitor • Design new module backplane and front panel to retrofit existing PATA/SATA Mark 5 modules for XCube compatibility (though must use only SATA disks); external cooling must be provided by user (can use Mark 5 chassis, for example)

  6. Recording Rate vs Time

  7. k$/Gbpsvs Time

  8. Backend-bandwidth price vs time

  9. Disk price vs time

  10. Plans • Continue to evaluate • Work with XCube to support VLBI-specific requirements • Plan to have a XCube demo system at May 2011 TOW meeting at Haystack • Work with XCube to develop business model compatible with VLBI community requirements • Current system will actually support ~12Gbps, and possibly 16Gbps by adding more 10GigE interfaces and another disk controller • Future upgrades to 32Gbps expected over next couple of years A comprehensive document by Michael Taveniku about the XCube system for VLBI is available.

  11. Questions?

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