SAS Technology by Ekta Gupta (6th sem, CS)

Every company, regardless of size, wants to be able to save money and have flexible mass storage equipment. When systems grow larger, making equipment choices can have a substantial impact on the bottom line. In enterprise server environments where cost, performance, benefits and architecture are key considerations, transitioning from parallel SCSI or ATA to SAS, provides the user unprecedented choices in storage solutions.

A way to keep costs lower and maintain flexibility is to transition to Serial Attached SCSI (SAS). Current server solutions are not very flexible with respect to the type of storage they deploy. Systems designers for direct-attached storage (DAS) must choose between a low-cost storage interconnect like parallel ATA, or a mainstream interconnect like parallel U320 SCSI. The SCSI Trade Association (STA) has recognized the benefit of SAS over its predecessor Ultra320 SCSI and has endorsed SAS technology as the future of mainstream SCSI.

SAS technology encompasses a set of innovations that changes the familiar parallel SCSI interconnect between a server and its storage devices. Along the way, SAS embraces the best features of other serial storage solutions and provides a roadmap for innovation and improvement now and into the future.

SAS supports dual-port and full duplex communication between servers and disk drives. It extends the reliability and bandwidth opportunities by using expanders to create wide ports, which are multi-path connections between the server and storage solutions. It also improves manageability of the storage solution by providing Serial Management Protocol (SMP) to monitor connections between individual devices and identify points of failure or reduced performance. This technology also uses a smaller interface connector, taking advantage of small form factor SAS drives, thus enabling the development of highly space-efficient and lower power server and storage drives.

By virtue of its multi-protocol support, a SAS-based storage solution will enable customers to deploy a standardized server interface and choose the most appropriate storage for their application. Low-cost SATA drives currently being used in desktop solutions will be available for less demanding applications, while enterprise-class SAS drives will provide the reliability and performance demanded of mainstream server applications. The native SAS protocol uses the familiar SCSI command set and aspects of the Fibre Channel (FC) transport layer, which prepares SAS for low-cost bridge solutions to FC or iSCSI Storage Area Networks (SANs) in the future.

SAS solutions complement mid-range to high-end enterprise servers and workstations using internal storage, direct attached storage (DAS) or network-attached storage (NAS). Flexibility provided by SAS allows customers to tailor storage for solutions that provide mixed pools of storage within cost constraints. End users benefit from the cost reductions that SAS/Serial ATA compatibility provides to back-plane manufacturers, system OEMs and VARs. The ability to change from SAS to SATA drives without purchasing new systems simplifies the upgrade process and helps hedge end-user investments on future technology advancements.

By designing in compatibility with SATA drives at the connector, SAS systems allow a lower cost SATA alternative to the higher reliability and performance of SAS drives. SAS systems communicate with the existing 1.5-Gb/s SATA drives as well as the high-speed serial, signaling of the new 3-Gb/s SAS drives--with potential speeds to 12-Gb/s. SAS also enhances the point-to-point SATA topology by incorporating expanders, which are low-cost switches that allow a significant number of SATA or SAS drives to be connected to the server.

SAS and SATA compatibility enables VARs and integrators to easily configure a system for an individual customer, simply by installing the preferred disk drives. VARs can focus on matching the processing and storage needs of the customer with fewer compromises because of storage interface limitations. There is no longer a need to worry about installing the proper backplane and cables. The reduced complexity and flexibility can improve the overall customer experience.

The compatibility between SAS and SATA has widespread benefits for enterprise users. One of the primary benefits of compatibility between SAS systems and SATA drives will be the ability to install a common infrastructure of cables, connectors, backplanes, cabinets and components. SAS leverages the SATA interconnect technology to have compatibility with lower cost drives.

SAS, as a point-to-point architecture, establishes a link directly from the controller to a disk drive or through an expander-switching matrix. However, in existing parallel SCSI, only two devices can communicate at once, and as throughput needs increase, the shared-access medium can become a bandwidth bottleneck which affects scalability. Shared access topologies also are typically more complex and have arbitration schemes that are more time consuming than point-to-point architectures.

Mobile Email Solutions Using Push Email and PIM Synchronization by Aditya Mishra (6th sem, EC)

1. An Introduction to Mobile Email
While the complexity and requirements that large scale solutions must achieve have greatly increased during the last few years, a growing number of service providers have also started to include support for enterprise functionalities in order to better meet and adapt to their customers’ ever changing messaging needs.

With email quickly becoming the primary means of communication for both corporate and individual users, the competition in the market also gets tougher every day. Consequently, a new breed of email services has to be appended to already existing portfolios in order to attract new customers and keep current service subscribers happy. This is where offering mobile email functionalities such as the Push technology or PIM database synchronization can make the difference.

2. Push Email and PIM Synchronization
Instant access to messages, contacts, calendar, or tasks regardless of time and location makes it easier for mobile workers to manage business operations, to stay in touch with customers and partners, and abreast of the latest changes and events on the market. It also ensures a better balance between professional and personal lives, enabling frequent travelers to keep in close contact with family and friends at all times. As a result, instant email retrieval has become more and more popular in both business and personal communication environments.

Smartphones and PDAs have also raised the bar in this sense and personal information management along with wireless (GPRS, 3G etc.) email access are visibly embraced by a fast-growing community of users. This is a known fact and the trend seems to pick up the pace with each month.

How It Works:
Email and PIM synchronization is the next best thing in email since the invention of the IMAP protocol. Through a technology, now known as “Push Email”, the tables have turned on email servers and clients. Normally, the client (desktop or mobile) would connect to the server and log in with the account credentials. Once the authentication is complete the client would poll the account by asking the server if any new messages are available.

As opposed to this, Push email instructs the server to instantly notify the client when a new email arrives. The main difference between these two approaches consists in the fact that the server will always know when a new message exists, while the client does not and has to check for them in a timely fashion. Push email is also much more economic in terms of data transfer amount and bandwidth usage. Establishing a single connection and maintaining it in an idle state is a very relaxed way to help the server contact the client whenever required.

Almost the same thing happens when speaking about PIM database synchronization. Appointments, tasks, notes and all of the data stored as PIM information are translated into email objects formatted in a special way, so that the contents can later be interpreted appropriately. So both emails and PIM data rely on the same standard and look a lot alike, despite some major differences that will not be detailed in the present whitepaper. What needs to be remembered is that from an email server’s perspective, the above mentioned objects are considered emails in the general meaning of the word.

3. AXIGEN Mobility Services
At this time, quite a lot of PIM sync and email pushing technologies exist and they are all implemented differently, even though they perform the same task. By far, the most popular technology, used world-wide, is Microsoft’s ActiveSync protocol. Therefore, AXIGEN has chosen to first implement support for this specific technology in order to reach and provide this feature to the largest base of users possible. The series of mobile devices and handsets that support the ActiveSync protocol includes Nokia / SymbianOS devices, Windows Mobile (since 2003 up to latest version), Apple iPhone and other devices that can have compatible software installed.