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NEXPReS WP8

This project aims to determine the best practical mix of solutions for high-bandwidth, high-capacity storage on demand. It will explore different storage options, packaging solutions, and connectivity methods to serve the needs of evolving VLBI data acquisition and processing. Participants include JIVE, ASTRON, INAF, UMAN, OSO, PSNC, and AALTO.

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NEXPReS WP8

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  1. NEXPReS WP8 Provisioning High-Bandwidth, High-Capacity Networked Storage on DemandAri MujunenBoard Meeting 20-Sep-2010 in Manchester Research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007- 2013) under grant agreement n° RI-261525. This presentation reflects only the author's views. The European Union is not liable for any use that may be made of the information contained therein.

  2. WP8 – High-bw+cap Storage on Demand Participants JIVE, ASTRON, INAF, UMAN, OSO, PSNC, AALTO Total person-months 163.2 Deliverables 12 (11 reports and one demonstration test)

  3. WP8 – GANTT Chart with % of 1FTEover Task Durations

  4. Partner Focus Areas AALTO Coordination, basic technologies ASTRON Long-term archival & reprocessing INAF Global/local allocation/deallocation schemes JIVE Augmenting correlation capabilities /w buffering OSO Trial-site performance & applicability testing PSNC Role & trials of computing center buffering UMAN Trial-site performance & applicability testing

  5. Start at Partners, First Deliverables AALTO Jul-2010 .. Dec-2010 (D8.1), .. Feb-2011 (D8.2), .. ASTRON Jul-2010/Oct-2011 .. Mar-2013 (D8.9) INAF Jul-2010 .. Apr-2011 (D8.3), .. May-2012 (D8.6) JIVE Jul-2010 .. Aug-2012 (D8.8), .. Feb-2013 (D8.10) OSO Feb-2011 .. Sep-2012 (in D8.4), .. Mar-2013 (in D8.5+7) PSNC Feb-2011 .. Sep-2012 (in D8.4), .. Mar-2013 (in D8.5+7) UMAN Feb-2011 .. Sep-2012 (in D8.4), .. Mar-2013 (in D8.5+7) ACTION: Send your POC's email to 'Ari.Mujunen@tkk.fi' for WP8 deliverables and execution of work!

  6. Objective Determine the best practical mix of solutions What kind of storage HDDs, SSDs, memory buffers, others Where located & packaged Geographically (stations, correlators, computing centers, clouds,...) Locally (enclosures, racks, packaging, net topologies,...) Connected in which ways Locally (interface types, net equipment,...), globally (ship, net, LP,...) How storage is allocated/deallocated and accessed Algorithms, APIs, sw structure; strategies to bookkeeping,... Which will serve the needs of evolving (>1Gbps) VLBI data acquisition and processing

  7. Model / Mindset Framework VLBI is globally geographically distributed data acquisition, data storage, and data processing Where data from a given global observation in time must be brought to one place to be compared / correlated => Implies data transfers geographically, globally Modelling the global VLBI network as a (potentially hierarchically) connected network of “nodules” Which have capabilities like connectivity (BW, IF types,..) storage (size, BW, BW dir limits,..), computing, etc. Which can be remodeled and replaced with new (hierarchical) “nodule” designs without affecting (too much) the “big picture”

  8. Nodules Pretty much any piece of equipment (Or a larger collection of such equipment, a “system”) Which can be described with a small set of capabilities Connectivity options and capabilities Interface types, bandwidths, bw / direction limitations Storage options and capabilities Device types, r/w bandwidths, bw /direction limitations, sw access methods Internal CPU, RAM buffering, and data “pumping” power Packaging options Price, power consumption, longevity,...

  9. Connectivity All sorts of methods used to transfer data from one place to another Physical shipping Networking (both local and global) Device interfaces (e.g. SATA II) Internal buses within equipment VLBI interfaces (e.g. legacy Mark IV formatter if) Connectivity has a given bandwith and its restrictions Direction, simultaneous use, less than theoretical performance in a given interconnect,...

  10. Existing “Nodules” Variants of Mark 5 5A, 5B: 1Gbps in or out /w shipping; 1.6Gbps in or out /w sw 5B+: 1/2Gbps in or out /w shipping; 3.2(?)Gbps in or out /w sw 5C: 4Gbps only in, /w shipping; 3.2(?)Gbps in or out /w sw Metsähovi 20-disk pack /w 10GE PC 6Gbps in or out /w shipping(?); 6Gbps in or out /w sw; in&out /w sw not yet tested BackBlaze 45-disk 4U rackmount /w 1(!)GE PC Emerging high-end 2-4-6U rackmounts Claim “up to” 16—24Gbps r/w at a premium price

  11. Nodule Jigsaw Puzzle For instance, try to find a balanced match of storage, connectivity, and packaging options to accompany ~CPU Storage Options 2—4 SATA II disks 6 SATA II disks 4Gbps(?) 4—6 SATA II disks + 5 /w PM = ~ 10 SATA II disks 20 SATA II disks /w PM 6Gbps 20—45 SATA II disks /w many controllers 8-10-??Gbps • Connectivity Options • 2 1GE ports • 1Gbps (or a little more) • 3 1GE ports • 2Gbps(?) • 1 10GE port • 6Gbps, maybe 8Gbps • 2 10GE ports • ?

  12. Packaging Puzzles Single unit Tend to become bulky; problems of (semi)custom construction Small-scale rack installation Full-size rack Rack connectivity: switches as 24/48 1GE x 2 10GE (cheap), 8 10GE, 24 10GE (rare, expensive, 10GE CX->T transition) Google-style “racks” Very economical for “20 or more small PCs” configuration But becomes trash in a couple of years and must be thrown away and replaced with a new set... Rack farms

  13. Simultaneous Read and Write Want to observe (and store a copy of data) and at the same time, already start processing Frequently dictated by the need to use the same (maybe special) connectivity for both directions Two problems: HDD seek time, slows down using more than one “spot” of disk Even without, double data streaming bandwidth required throughout the internal data paths Seek alleviated by multiplexing HDDs Means more HDDs needed than the bare minimum Multiplexing typically in time, in time chunks >>HDD seek time

  14. Imagining the NEXPReS WP8 Nodule... We want more than a trivial single-PC system But not any large-scale rack systems (no money for that!) Something that would retain its topology in 2015 But go from 4—8Gbps (NEXPReS) to 16—32Gbps (2015) The most obvious Nodule would be a configuration of six 1GE PCs and one 24 1GE-to-(1 or 2)10GE switch Could do 4Gbps in or out, 1—2Gbps in and out simultaneously Can exercise multiplexing in time and IP, and multiple nets/PC The obvious upgrade in 2015 would be to 100% 10GE Which means everything---except software! Might get up to 32Gbps in or out...

  15. Imagining the NEXPReS WP8 Nodule... OTOH, a station Nodule could be a configuration of two 10GE PCs and one small 10GE switch Could do 8Gbps in or out, 4Gbps in and out simultaneously Can exercise multiplexing in time and IP The obvious upgrade in 2015 would be to buy more similar PCs But then: PCs of 2015 will be completely different—a mixed configuration might look weird and make use (=software) more complicated; the 10GE switch might prove too small and outdated So might end up buying all new stuff anyway... Will quite likely cost now more than the “six small PCs” scenario Well, this should be in the Dec-2010 D8.1 deliverable...

  16. “The Inconvenient Truths” :-) About e-VLBI: “A given station cannot really sustain recording bandwidth larger than their e-VLBI connectivity—unless given an unlimited disk buffer.” “A single slow (or high-latency like shipping) connection in a given e-VLBI network will force others (or some buffering party) to buffer most of the VLBI data, if not all.” About buffers and archives: “Huge disk buffers with thousands of disks (whether distributed or centralized) will cost a fortune, age rapidly, and be fragile (even with the highest-end equipment) and in constant need of (hw) maintenance.”

  17. “The Inconvenient Truths” :-) About Mark 5s: “The existing 8-packs of PATA disks will never be accessed simultaneously read and write—unless Conduant dramatically changes StreamStor firmware.” “No variant of Mark 5 will ever feed the Mark IV correlator faster than 1Gbps. While a given Mark 5 unit is feeding the correlator, no new data can be fed into that Mark 5 at the same time.” “At 1.6Gbps and maybe 3.2Gbps in pairs, the existing 8-PATA-packs make little sense in >=4Gbps buffering. 8-packs will continue to be useful only for storing data certainly destined to be shipped physically.”

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