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- Monti, Paolo, 1973-, et al.
(författare)
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Restoring optical cloud services using relocation
- 2014
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Konferensbidrag (refereegranskat)abstract
- Optical cloud is a very popular concept by which storage and computing resources (i.e., IT resources) are distributed over different datacenter (DC) locations interconnected via high-speed optical wavelength division multiplexing (WDM) links. In this paradigm cloud services are provisioned in an anycast fashion, where only the source node needs to be specified in the routing and resource assignment phase, while any DC (with enough IT resources) can be used to accommodate a cloud service. Anycast provisioning has a number of advantages already recognized by optical cloud providers [1][2]. This kind of provisioning paradigm allows, for example, for the live relocation of the already provisioned cloud services, referred to as the service relocation concept. It means that if the DC location is not essential for the execution of a certain cloud service, multiple relocations of the job to other DC locations are possible. This allows for a more efficient management of both the cloud and the transport network resources. Service relocation has also the potential to bring an extra degree of flexibility to survivability strategies. By providing the option for relocating a cloud service it is possible to use a backup path terminating at a DC that is different from the one used by the primary path. This benefit has been assessed in the literature showing the ability to improve resources efficiency by using service relocation in conjunction with path protection strategies [1]. Another instance in which service relocation might be beneficial is when it is combined with restoration-based survivability strategies. These strategies are very efficient in using backup resources, i.e., they are dynamically provisioned only upon a failure, but restoration-based approaches suffer from a certain risk that the backup network resources might not be available when needed [3]. Service relocation can potentially alleviate this problem. This talk presents a study where the objective is to inves- igate if relocating a cloud service disrupted by a network failure is beneficial in terms of both restorability and average connection availability. To this end the talk will present a number of results based on the solution of an efficient and scalable heuristic algorithm able to jointly solve the restoration and service relocation problem. These results are also benchmarked against the performance of an integer linear programming (ILP) model [4] optimizing the same objective function as the heuristic. In summary it can be concluded that by using relocation the average service availability can be significantly improved requiring only a minimal fraction of the cloud services to be relocated. In addition the proposed heuristic behaves very closely to the optimal ILP results in terms of both restorability and average connection availability.
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| 2. |
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| 3. |
- Troll, Valentin, et al.
(författare)
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Pre-Teide Volcanic Activity on the Northeast Volcanic Rift Zone
- 2013
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Ingår i: Teide Volcano. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642258923 - 9783642258930 ; , s. 75-92
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Bokkapitel (refereegranskat)abstract
- The northeast rift zone of Tenerife (NERZ) presents a partially eroded volcanic rift that offers a superb opportunity to study the structure and evolution of oceanic rift zones. Field data, structural observations, isotopic dating, magnetic stratigraphy, and isotope geochemistry have recently become available for this rift and provide a reliable temporal framework for understanding the structural and petrological evolution of the entire rift zone. The NERZ appears to have formed in several major pulses of activity with a particularly high production rate in the Pleistocene (ca. 0.99 and 0.56 Ma). The rift underwent several episodes of flank creep and eventual catastrophic collapses driven by intense intrusive activity and gravitational adjustment. Petrologically, a variety of mafic rock types, including crystal-rich ankaramites, have been documented, with most samples isotopically typical of the “Tenerife signal”. Some of the NERZ magmas also bear witness to contamination by hydrothermally altered components of the island edifice and/or sediments. Isotope geochemistry furthermore points to the generation of the NERZ magmas from an upwelling column of mantle plume material mixed with upper asthenospheric mantle. Finally, persistent isotopic similarity through time between the NERZ and the older central edifices on Tenerife provides strong evidence for a genetic link between Tenerife’s principal volcanic episodes.
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| 4. |
- Wiesmaier, Sebastian, et al.
(författare)
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Magma Mixing in the 1100 AD Montaña Reventada Composite Lava Flow : Interaction of Rift Zone and Central Complex Magmatism
- 2013
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Ingår i: Teide Volcano. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642258923 - 9783642258930 ; , s. 191-211
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Bokkapitel (refereegranskat)abstract
- Zoned eruption deposits frequently show a lower felsic and an upper maficmember, thought to reflect eruption from a large, stratified magmachambers. In contrast, however, the Montaña Reventada composite flow inTenerife consists of a lower basanite and a much thicker upper phonolite. Asharp interface separates the basanite and phonolite, and a chilled margin atthis contact indicates the basanite was still hot upon emplacement of thephonolite, i.e. the two magmas erupted in very quick succession. Threetypes of mafic to intermediate inclusions are found in the phonolite, whichcomprise foamy quenched ones, inclusions with chilled margins and thosethat are physically mingled, reflecting progressive mixing with adecreasing temperature contrast between the end-member magmasinvolved. Analysis of basanite, phonolite and inclusions for majors, tracesand Sr, Nd and Pb isotopes show the inclusions to be derived from binarymixing of basanite and phonolite end-members in ratios of 2:1–4:1.Although basanite and phonolite magmas were erupted in quick succession, contrasting206Pb/204Pb ratios show them to be geneticallydistinct. The Montaña Reventada basanite and phonolite first came intocontact just prior to eruption and had seemingly limited interaction time.Montaña Reventada erupted from the transition zone between twoplumbing systems, the phonolitic Teide-Pico Viejo complex and thebasanitic Northwest rift zone. A rift zone basanite dyke most likelyintersected a previously emplaced phonolite magma pocket, leading toeruption of geochemically and texturally unaffected basanite, followed byinclusion-rich phonolite that exploited the already established conduit.
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| 5. |
- Wiesmaier, Sebastian, et al.
(författare)
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Magma mixing in the 1100 AD Montaña Reventada composite lava flow, Tenerife, Canary Islands : Interaction between rift zone and central volcano plumbing systems
- 2011
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Ingår i: Contributions to Mineralogy and Petrology. - : Springer. - 0010-7999 .- 1432-0967. ; 162:3, s. 651-669
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Tidskriftsartikel (refereegranskat)abstract
- Zoned eruption deposits commonly show a lower felsic and an upper mafic member, thought to reflect eruption from large, stratified magma chambers. In contrast, the Montaña Reventada composite flow (Tenerife) consists of a lower basanite and a much thicker upper phonolite. A sharp interface separates basanite and phonolite, and chilled margins at this contact indicate the basanite was still hot upon emplacement of the phonolite, i.e. the two magmas erupted in quick succession. Four types of mafic to intermediate inclusions are found in the phonolite. Inclusion textures comprise foamy quenched ones, others with chilled margins and yet others that are physically mingled, reflecting progressive mixing with a decreasing temperature contrast between the end-members. Analysis of basanite, phonolite and inclusions for majors, traces and Sr, Nd and Pb isotopes show the inclusions to be derived from binary mixing of basanite and phonolite end-members in ratios of 2:1 to 4:1. Although, basanite and phonolite magmas were in direct contact, contrasting 206Pb/204Pb ratios show that they are genetically distinct (19.7193(21)–19.7418(31) vs. 19.7671(18)–19.7807(23), respectively). We argue that the Montaña Reventada basanite and phonolite first met just prior to eruption and had limited interaction time only. Montaña Reventada erupted from the transition zone between two plumbing systems, the phonolitic Teide-Pico Viejo complex and the basanitic Northwest rift zone. A rift zone basanite dyke most likely intersected the previously emplaced phonolite magma chamber. This led to eruption of geochemically and texturally unaffected basanite, with the inclusion-rich phonolite subsequently following into the established conduit.
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| 6. |
- Wiesmaier, Sebastian, et al.
(författare)
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Magmatic Differentiation in the Teide–Pico Viejo Succession : Isotope Analysis as a Key to Deciphering the Origin of Phonolite Magma
- 2013
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Ingår i: Teide Volcano. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642258923 - 9783642258930 ; , s. 173-190
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Bokkapitel (refereegranskat)abstract
- In Tenerife, lavas of the recent Teide–Pico Viejo central complex show a marked bimodality in composition from initially mafic lava (200–30 ka) to highly differentiated phonolite (30–0 ka). Groundmass Sr–Nd–Pb–O and feldspar 18O data demonstrate open system behaviour for the petrogenesis of Teide–Pico Viejo felsic lavas, but contamination by ocean sediment can be excluded due to the low 206Pb/204Pb ratios of North Atlantic sediment. Isotope mixing hyperbolae require an assimilant of predominantly felsic composition for the Teide–Pico Viejo succession. Unsystematic and heterogeneous variation of 18O in fresh and unaltered feldspars across the Teide–Pico Viejo succession indicates magmatic addition of diverse 18O assimilants, best matched by nepheline syenites that occur as fresh and altered lithic blocks in voluminous pre-Teide ignimbrite deposits. Rare earth element modelling indicates that nepheline syenite needs to be melted in bulk to form a suitable end-member composition. Energy-Constrained Assimilation Fractional Crystallisation (EC-AFC) modelling reproduces the bulk of the succession, which implies that the petrogenesis of Teide–Pico Viejo lavas is governed by the coupled assimilation of nepheline syenite during fractional crystallisation. The most differentiated (and most radiogenic) lava computes to >97.8 % assimilant, likely represented by a nepheline syenite bulk melt that formed by underplating with juvenile mafic material. These recent research developments therefore recognise a wider variability of magmatic differentiation processes at Teide–Pico Viejo than previously considered.
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