HetFS: A heterogeneous file system for everyone

Storage devices have been getting more and more diverse during the last decade. The advent of SSDs made it painfully clear that rotating devices, such as HDDs or magnetic tapes, were lacking in regards to response time. However, SSDs currently have a limited number of write cycles and a significantly larger price per capacity, which has prevented rotational technologies from begin abandoned. Additionally, Non-Volatile Memories (NVMs) have been lately gaining traction, offering devices that typically outperform NAND-based SSDs but exhibit a full new set of idiosyncrasies. Therefore, in order to appropriately support this diversity, intelligent mechanisms will be needed in the near-future to balance the benefits and drawbacks of each storage technology available to a system. In this paper, we present a first step towards such a mechanism called HetFS, an extension to the ZFS file system that is capable of choosing the storage device a file should be kept in according to preprogrammed filters. We introduce the prototype and show some preliminary results of the effects obtained when placing specific files into different devices.The research leading to these results has received funding from the European Community under the BIGStorage ETN (Project 642963 of the H2020-MSCA-ITN-2014), by the Spanish Ministry of Economy and Competitiveness under the TIN2015-65316 grant and by the Catalan Government under the 2014-SGR- 1051 grant. To learn more about the BigStorage project, please visit http: //bigstorage-project.eu/.Peer ReviewedPostprint (author's final draft

Path Processing using Solid State Storage

Recent advances in solid state technology have led to the introduction of Solid State Drives (SSDs). Todays SSDs store data persistently using NAND flash memory. While SSDs are more expensive than hard disks when measured in dollars per gigabyte, they are significantly cheaper when measured in dollars per random I/O per second. Additional storage technologies are under development, Phase Change Memory (PCM) being the next one to enter the marketplace. PCM is nonvolatile, it can be byte-addressable, and in future Multi Level Cell (MLC) devices, PCM is expected to be denser than DRAM. PCM has lower read and write latency compared to NAND flash memory, and it can endure orders of magnitude more write cycles before wearing out. Recent research has shown that solid state devices can be particularly beneficial for latency-bound applications involving dependent reads. Latency-bound applications like path processing in the context of graph processing or Resource Description Framework (RDF) data processing are typical examples of these applications. We demonstrate via a custom graph benchmark that even an early prototype Phase Change Memory device can offer significant improvements over mature flash devices (1.5x - 2.5x speedup in response times). We take this observation further by building Pythia, a prototype RDF repository tailor-made for Solid State Storage to investigate the predicted benefits for these type of workloads that can be achieved in a properly designed RDF repository. We compare the performance of our repository against the state of the art RDF-3X repository in a limited set of tests and discuss the results. We finally compare the performance of our repository running on a PCM-based device against a state of the art flash device, showing that there is indeed significant gain to be achieved by using PCM for RDF processing

Routes for breaching and protecting genetic privacy

We are entering the era of ubiquitous genetic information for research, clinical care, and personal curiosity. Sharing these datasets is vital for rapid progress in understanding the genetic basis of human diseases. However, one growing concern is the ability to protect the genetic privacy of the data originators. Here, we technically map threats to genetic privacy and discuss potential mitigation strategies for privacy-preserving dissemination of genetic data.Comment: Draft for comment

Lack of association between plasma leptin levels and appetite in children with iron deficiency

PubMedID: 11448591A negative correlation between leptin and appetite or food intake has been shown in healthy individuals. However, the role of leptin in clinical conditions characterized by anorexia has not been established. One of the well-known clinical features of iron-deficiency anemia is poor appetite. We examined the changes in plasma leptin levels in relation to expected improvement in appetite with iron treatment in children with iron deficiency. In 24 infants and small children (mean age ± standard deviation = 19.6 ± 7.7 months) with iron deficiency, we studied plasma leptin levels before and after iron therapy. After 15.0 ± 2.4 wk of iron treatment, serum ferritin levels improved significantly, with accompanying increases in their subjective appetite scores and food intakes. However, as their mean age and plasma leptin levels adjusted their body mass indexes were unchanged. Serum ferritin correlated significantly with appetite score (r = 0.680, P < 0.001) and food intake (r = 0.480, P < 0.01). Leptin correlated only with body mass index (r = 0.405, P < 0.01). Lack of association between plasma leptin levels and degree of appetite in iron-deficient children treated with iron suggests a leptin-independent mechanism for the observed increase in appetite. Copyright © 2001 Elsevier Science Inc