Evaluating the Upper Bound of Energy Cost Saving by Proactive Data Center Management
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT
Authors: Milocco, Ruben; Minet, Pascale; Renault, Eric; Boumerdassi, Selma
Abstract
Data Centers (DCs) need to periodically configure their servers in order to meet user demands. Since appropriate proactive management to meet demands reduces the cost, either by improving Quality of Service (QoS) or saving energy, there is a great interest in studying different proactive strategies based on predictions of the energy used to serve CPU and memory requests. The amount of savings that can be achieved depends not only on the selected proactive strategy but also on user-demand statistics and the predictors used. Despite its importance, it is difficult to find theoretical studies that quantify the savings that can be made, due to the problem complexity. A proactive DC management strategy is presented together with its upper bound of energy cost savings obtained with respect to a purely reactive management. Using this method together with records of the recent past, it is possible to quantify the efficiency of different predictors. Both linear and nonlinear predictors are studied, using a Google data set collected over 29 days, to evaluate the benefits that can be obtained with these two predictors.
Plasmacytoid dendritic cells cross-prime naive CD8 T cells by transferring antigen to conventional dendritic cells through exosomes
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Authors: Fu, Chunmei; Peng, Peng; Loschko, Jakob; Feng, Li; Phuong Pham; Cui, Weiguo; Lee, Kelvin P.; Krug, Anne B.; Jiang, Aimin
Abstract
Although plasmacytoid dendritic cells (pDCs) have been shown to play a critical role in generating viral immunity and promoting tolerance to suppress antitumor immunity, whether and how pDCs cross-prime CD8 T cells in vivo remain controversial. Using a pDC-targeted vaccine model to deliver antigens specifically to pDCs, we have demonstrated that pDC-targeted vaccination led to strong cross-priming and durable CD8 T cell immunity. Surprisingly, cross-presenting pDCs required conventional DCs (cDCs) to achieve cross-priming in vivo by transferring antigens to cDCs. Taking advantage of an in vitro system where only pDCs had access to antigens, we further demonstrated that cross-presenting pDCs were unable to efficiently prime CD8 T cells by themselves, but conferred antigennaive cDCs the capability of cross-priming CD8 T cells by transferring antigens to cDCs. Although both cDC1s and cDC2s exhibited similar efficiency in acquiring antigens from pDCs, cDC1s but not cDC2s were required for cross-priming upon pDC-targeted vaccination, suggesting that cDC1s played a critical role in pDC-mediated cross-priming independent of their function in antigen presentation. Antigen transfer from pDCs to cDCs was mediated by previously unreported pDC-derived exosomes (pDCexos), that were also produced by pDCs under various conditions. Importantly, all these pDCexos primed naive antigen-specific CD8 T cells only in the presence of bystander cDCs, similarly to cross-presenting pDCs, thus identifying pDCexo-mediated antigen transfer to cDCs as a mechanism for pDCs to achieve cross-priming. In summary, our data suggest that pDCs employ a unique mechanism of pDCexo-mediated antigen transfer to cDCs for cross-priming.