Serial vs Parallel

Why Serial is taking over Parallel Communication?

We have seen the wide spread of USB peripherals, using PCIe over conventional PCI and long ethernet cables... All these represent the approach towards Serial Communication...

Define:

Serial: transfer a bit at a time.

Parallel: transfer multi bits at a time as the number of lanes.

Discuss:

Parallel Communication suffer from the following against Serial Communication:

-More Processing: "takes more time"

-Signal Skewing: due to imperfections in cables, may be a bit would be delayed to others.

-Cross Talking: Signals affects other signals due to magnetic fields resulted from high resonance " not reliable for long distances".

-Larger Size, more cost.

Conclusion:

With the increasing clock speed of the processor:

Parallel transferring becomes not immune to noise especially for long distances, has higher SNR, and less BW.

Serial transferring is much faster, immune to noise, longer distance, and I think easier to program.

Parallel Communication would overcome all these vices if the speed of its data transferring is multiple the speed of Serial Communication and reliable.

However:

As the multi-core processors are being exposed and the clock speed is increasingly higher, the need of parallel applications serial advantageous is vital

A good article to be read at http://www.computerworld.com/s/article/87095/Serial_vs._Parallel_Storage

SRAM vs DRAM

I would like to share this info with you about Static and Dynamic Ram:

• SRAM multi transistors per bit whereas DRAM uses one transistor and two capacitors per bit.
• DRAM needs to periodically refreshed "recharged" in order to maintain its value. That is why it is called dynamic.
• SRAM is faster compared to DRAM
• SRAM consumes less power than DRAM
• SRAM is more expensive than DRAM
• Cheaper DRAM is used in main memory while SRAM is commonly used in cache memory

ِAgile Approach

I liked this humanistic based Development

"Individuals and interactions over processes and tools
Working software over comprehensive documentation
Customer collaboration over contract negotiation
Responding to change over following a plan" [1]

[1]Beck, Kent; et al. (2001). "Manifesto for Agile Software Development". Agile Alliance. Retrieved 2010-06-14

PfSense for Load Balance and MultiWan

Many Articles in the web telling how to make Multi Wan Connection for load balancing; one of them http://doc.pfsense.org/index.php/MultiWanVersion1.2

It actually describes the procedure well but one of the problem you would find when one of the WAN lines fail, there will be no Internet connection.

The reason is not because LoadBalancing fails but because DNS servers were not identified in the DHCP service.

Also I have to highlight that for Firewall rules...

• Rules are evaluated in Top-Down approach at first match basis where there is a DenyAll is hidden in the most down .
• Uses state; that means if a user requests a service from outside and it is permitted in the inside inteface, no need for declaring a rule in the outside interface.
• Rules are identified in the inbound direction of interfaces.

CARP

"Common Address Redundancy Protocol" = Clustering

• More redundancy for high availability.
• Originally deployed under FreeBSD.
• Seen when installing and configuring PfSense firewall.

No restart again for completing updates

The real meaning of HA is done through ksplice

Have you ever get annoyed because you are in the middle of work and your operating system asks you repetitively to rsetart to apply updates?

with Ksplice, no restart is required. It does an in-memory operation to update kernel.

Many definition would be changed of service management such as testing/development environment and production environment for applying patches.

It is free for Ubuntu user editions and costs nearly 4$ a month for server editions.

have a look: http://www.ksplice.com/

Statement

The world tends to be fictionable...

Tricorder, Claytronics, Nanorobots....

Will I have a hand on these???!