Performance comparison between iSCSI and other hardware and software solutions

We report on our investigations on some technologies that can be used to build disk servers and networks of disk servers using commodity hardware and software solutions. It focuses on the performance that can be achieved by these systems and gives measured figures for different configurations. It is divided into two parts : iSCSI and other technologies and hardware and software RAID solutions. The first part studies different technologies that can be used by clients to access disk servers using a gigabit ethernet network. It covers block access technologies (iSCSI, hyperSCSI, ENBD). Experimental figures are given for different numbers of clients and servers. The second part compares a system based on 3ware hardware RAID controllers, a system using linux software RAID and IDE cards and a system mixing both hardware RAID and software RAID. Performance measurements for reading and writing are given for different RAID levels.Comment: Paper associated to a poster from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, LaTeX. PSN TUDP00

Health implications of an immigration raid: findings from a Latino community in the midwestern United States.

Immigration raids exemplify the reach of immigration law enforcement into the lives of Latino community members, yet little research characterizes the health effects of these raids. We examined the health implications of an immigration raid that resulted in multiple arrests and deportations and occurred midway through a community survey of a Latino population. We used linear regression following principal axis factoring to examine the influence of raid timing on immigration enforcement stress and self-rated health. We controlled for age, sex, relationship status, years in the county in which the raid occurred, children in the home, and nativity. 325 participants completed the survey before the raid and 151 after. Completing the survey after the raid was associated with higher levels of immigration enforcement stress and lower self-rated health scores. Findings indicate the negative impact of immigration raids on Latino communities. Immigration discussions should include holistic assessments of health.UL1 TR000433 - NCATS NIH HH

Multi-Terabyte EIDE Disk Arrays running Linux RAID5

High-energy physics experiments are currently recording large amounts of data and in a few years will be recording prodigious quantities of data. New methods must be developed to handle this data and make analysis at universities possible. Grid Computing is one method; however, the data must be cached at the various Grid nodes. We examine some storage techniques that exploit recent developments in commodity hardware. Disk arrays using RAID level 5 (RAID-5) include both parity and striping. The striping improves access speed. The parity protects data in the event of a single disk failure, but not in the case of multiple disk failures. We report on tests of dual-processor Linux Software RAID-5 arrays and Hardware RAID-5 arrays using a 12-disk 3ware controller, in conjunction with 250 and 300 GB disks, for use in offline high-energy physics data analysis. The price of IDE disks is now less than $1/GB. These RAID-5 disk arrays can be scaled to sizes affordable to small institutions and used when fast random access at low cost is important.Comment: Talk from the 2004 Computing in High Energy and Nuclear Physics (CHEP04), Interlaken, Switzerland, 27th September - 1st October 2004, 4 pages, LaTeX, uses CHEP2004.cls. ID 47, Poster Session 2, Track

Pattern formation and optimization in army ant raids

Army ant colonies display complex foraging raid patterns involving thousands of individuals communicating through chemical trails. In this paper we explore, by means of a simple search algorithm, the properties of these trails in order to test the hypothesis that their structure reflects an optimized mechanism for exploring and exploiting food resources. The raid patterns of three army ant species, {em Eciton hamatum}, {em Eciton burchelli} and {em Eciton rapax}, are analysed. The respective diets of these species involve large but rare, small but common, and a combination of large but rare and small but common, food sources. Using a model proposed by Deneubourg and collaborators, we simulate the formation of raid patterns in response to different food distributions. Our results indicate that the empirically observed raid patterns maximise return on investment, that is, the amount of food brought back to the nest per unit of energy expended, for each of the diets. Moreover, the values of the parameters that characterise the three optimal pattern-generating mechanisms are strikingly similar. Therefore the same behavioural rules at the individual level can produce optimal colony-level patterns. The evolutionary implications of these findings are discussed.Postprint (published version