Simulation to scale of the HELIOS system

Within the space of a few years, IT companies with need for large-scale datacenters are considering alternatives to building traditional central datacenter facility. They have embraced a modular datacenter (also called pod, a smaller mobile datacenter) as the building block for reasons such as efficient cooling, power savings, mobility, easier deployment and administration. However, delivering scalable inter-pod bisection bandwidth remains a challenge. Current solutions that promise full bisection bandwidth between arbitrary pair of hosts can be expensive and power-intensive for interconnecting modular datacenters. Our recent work [FPR+10] proposed Helios, a scalable switch architecture for interconnecting modular datacenters using a hybrid core switch array consisting of electrical and optical switches. We show that Helios delivers a significant reduction in cost, cabling complexity, and power while providing scalable on-demand bandwidth to the communicating pair of hosts. In this thesis, we propose a TCP flow-based simulator for the Helios architecture. We describe the design/implementation, and validate the correct behavior of the simulator with the testbed execution of Helios prototype. We then evaluate the performance of Helios system against a variety of parameters - like scale (number of pods), link aggregation, and the composition of the core switch array - for differing communication patterns. The primary goal of this tool is to provide insights into how Helios might scale. Possible applications of this tool include network planning, searching newer optimizations, identifying bad application performance, planning VM migration such that the VMs better utilize Helios infrastructur

PortLand: A Scalable Fault-Tolerant Layer 2 Data Center Network Fabric

This paper considers the requirements for a scalable, easily manageable, fault-tolerant, and efficient data center network fabric. Trends in multi-core processors, end-host virtualization, and commodities of scale are pointing to future single-site data centers with millions of virtual end points. Existing layer 2 and layer 3 network protocols face some combination of limitations in such a setting: lack of scalability, difficult management, inflexible communication, or limited support for virtual machine migration. To some extent, these limitations may be inherent for Ethernet/IP style protocols when trying to support arbitrary topologies. We observe that data center networks are often managed as a single logical network fabric with a known baseline topology and growth model. We leverage this observation in the design and implementation of PortLand, a scalable, fault tolerant layer 2 routing and forwarding protocol for data center environments. Through our implementation and evaluation, we show that PortLand holds promise for supporting a “plug-and-play ” large-scale, data center network. Categories and Subject Descriptors C.2.1 [Network Architecture and Design]: communications; C.2.2 [Network Protocols]

Helios: A Hybrid Electrical/Optical Switch Architecture for Modular Data Centers

The basic building block of ever larger data centers has shifted from a rack to a modular container with hundreds or even thousands of servers. Delivering scalable bandwidth among such containers is a challenge. A number of recent efforts promise full bisection bandwidth between all servers, though with significant cost, complexity, and power consumption. We present Helios, a hybrid electrical/optical switch architecture that can deliver significant reductions in the number of switching elements, cabling, cost, and power consumption relative to recently proposed data center network architectures. We explore architectural trade offs and challenges associated with realizing these benefits through the evaluation of a fully functional Helios prototype

PortLand: A Scalable Fault-Tolerant Layer 2 Data Center Network Fabric

This paper considers the requirements for a scalable, easily manageable, fault-tolerant, and efficient data center network fabric. Trends in multi-core processors, end-host virtualization, and commodities of scale are pointing to future single-site data centers with millions of virtual end points. Existing layer 2 and layer 3 network protocols face some combination of limitations in such a setting: lack of scalability, difficult management, inflexible communication, or limited support for virtual machine migration. To some extent, these limitations may be inherent for Ethernet/IP style protocols when trying to support arbitrary topologies. We observe that data center networks are often managed as a single logical network fabric with a known baseline topology and growth model. We leverage this observation in the design and implementation of PortLand, a scalable, fault tolerant layer 2 routing and forwarding protocol for data center environments. Through our implementation and evaluation, we show that PortLand holds promise for supporting a “plug-and-play” large-scale, data center network

Efficacy and tolerability of fixed dose combination of metoprolol and amlodipine in Indian patients with essential hypertension

Background: This open-labeled, post-marketing study was conducted to assess the efficacy and tolerability of fixed dose combination of amlodipine and metoprolol extended release capsules in mild to moderate hypertension in adult Indian patients. Materials and Methods: Of 101 enrolled patients, 64 drug naοve patients were treated with regimen A (amlodipine 5 mg + metoprolol 25 mg) and those with prior history of hypertension ( n = 37) were treated with regimen B (amlodipine 5 mg + metoprolol 50 mg) for 8 weeks. Treatment response was assessed at week 4 and 8. Dose up titration to regimen B was carried out for those who failed to achieve the target blood pressure (BP) at week 4 in regimen A and additional antihypertensives were added to those in regimen B. Safety laboratory tests were performed at baseline and end of study. Results: Mean age (±SD) of patients was 53.36 (±11.26) years and body weight (±SD) 63.40 (10.03) kg. Ninety five patients (94.06%) were only hypertensive and 6 (5.94%) had hypertension with history of coronary artery disease; mean duration (±SD) of hypertension was 42.50 (48.07) months. At baseline, patients had a mean (±SD) systolic blood pressure (SBP) and diastolic blood pressure (DBP) of 154.98 (±7.76) mmHg and 95.55 (±5.70) mmHg respectively. There was a statistically significant ( P < 0.001) reduction of 12.16% and 14.69% in SBP, 11.49% and 14.65% in DBP at week 4 and week 8 respectively, compared to baseline. Normalization of overall BP was achieved in 49.49% and 70.71% patients at week 4 and 8, respectively. Peripheral edema was reported in 2.97% (3/101) patients. Conclusion: This combination was safe, efficacious, and well-tolerated in study population