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SSD and HDD: Advantages and Disadvantages

January 30 2018 , Written by Cisco & Cisco Router, Network Switch Published on #Networking, #IT, #Technology

How to choose between a traditional hard drive and a solid-state drive in your next PC?

In the following part we’d like share the detailed analysis of SSD and HDD that tells you the history of HDDs and SSDs, advantages and disadvantages, Hybrid Drives and Dual-Drive Systems and the Storage of tomorrow.

The original reviews from https://www.pcmag.com/article2/0,2817,2404258,00.asp

Until recently, PC buyers had very little choice about what kind of storage to get in a laptop or desktop. If you bought an ultraportable, you likely had a solid-state drive (SSD) as the primary drive (C: on Windows, Macintosh HD on a Mac). Every other desktop or laptop form factor had a hard disk drive (HDD). Now, you can configure most systems with either an HDD or an SSD, or in some cases both. But how do you choose? We explain the differences between SSDs and HDDs (or hard drives), and walk you through the advantages and disadvantage of both to help you decide.

An SSD does functionally everything a hard drive does, but data is instead stored on interconnected flash memory chips that retain the data even when there's no power present. The chips can either be permanently installed on the system's motherboard (as on some small laptops and ultraportables), on a PCI Express (PCIe) card (in some high-end workstations and an increasing number of bleeding-edge consumer systems), or in a box that's sized, shaped, and wired to slot in for a laptop or desktop's hard drive (common on everything else). These flash memory chips are of a different type than is used in USB thumb drives, and are typically faster and more reliable. SSDs are consequently more expensive than USB thumb drives of the same capacities.

Both SSDs and hard drives do the same job: They boot your system, and store your applications and personal files. But each type of storage has its own unique feature set. How do they differ, and why would you want to get one over the other?

Price: SSDs are more expensive than hard drives in terms of dollar per gigabyte. A 1TB internal 2.5-inch hard drive costs between $40 and $50, but as of this writing, an SSD of the same capacity and form factor starts at $250. That translates into 4 to 5 cents per gigabyte for the hard drive and 25 cents per gigabyte for the SSD. Since hard drives use older, more established technology, they will remain less expensive for the near future. Those extra hundreds for the SSD may push your system price over budget.

Maximum and Common Capacity: Although consumer-based SSD units top out at 4TB, those are still rare and expensive. You're more likely to find 500GB to 1TB units as primary drives in systems. While 500GB is considered a "base" hard drive in 2017, pricing concerns can push that down to 128GB for lower-priced SSD-based systems. Multimedia users will require even more, with 1TB to 4TB drives common in high-end systems. Basically, the more storage capacity, the more stuff you can keep on your PC. Cloud-based (Internet) storage may be good for housing files you plan to share among your phone, tablet, and PC, but local storage is less expensive, and you only have to buy it once.

Speed: This is where SSDs shine. An SSD-equipped PC will boot in less than a minute, and often in just seconds. A hard drive requires time to speed up to operating specs, and will continue to be slower than an SSD during normal use. A PC or Mac with an SSD boots faster, launches and runs apps faster, and transfers files faster. Whether you're using your computer for fun, school, or business, the extra speed may be the difference between finishing on time and failing.

Fragmentation: Because of their rotary recording surfaces, hard drives work best with larger files that are laid down in contiguous blocks. That way, the drive head can start and end its read in one continuous motion. When hard drives start to fill up, large files can become scattered around the disk platter, causing the drive to suffer from what's called fragmentation. While read/write algorithms have improved to the point that the effect is minimized, hard drives can still become fragmented. SSDs can't, however, because the lack of a physical read head means data can be stored anywhere. Thus, SSDs are inherently faster.

Durability: An SSD has no moving parts, so it is more likely to keep your data safe in the event you drop your laptop bag or your system is shaken about by an earthquake while it's operating. Most hard drives park their read/write heads when the system is off, but they are flying over the drive platter at a distance of a few nanometers when they are in operation. Besides, even parking brakes have limits. If you're rough on your equipment, an SSD is recommended.

Availability: Hard drives are more plentiful in budget and older systems, but SSDs are becoming more prevalent in recently released laptops. That said, the product lists from Western Digital, Toshiba, Seagate, Samsung, and Hitachi are still skewed in favor of hard drive models over SSDs. For PCs and Mac desktops, internal hard drives won't be going away completely, at least for the next few years. SSD model lines are growing in number: Witness the number of thin laptops with 256 to 512GB SSDs installed in place of hard drives.

Form Factors: Because hard drives rely on spinning platters, there is a limit to how small they can be manufactured. There was an initiative to make smaller 1.8-inch spinning hard drives, but that's stalled at about 320GB, since the phablet and smartphone manufacturers have settled on flash memory for their primary storage. SSDs have no such limitation, so they can continue to shrink as time goes on. SSDs are available in 2.5-inch laptop drive-sized boxes, but that's only for convenience. As laptops continue to become slimmer and tablets take over as primary platforms for Web surfing, you'll start to see the adoption of SSDs skyrocket.

Noise: Even the quietest hard drive will emit a bit of noise when it is in use from the drive spinning or the read arm moving back and forth, particularly if it's in a system that's been banged about or if it's been improperly installed in an all-metal system. Faster hard drives will make more noise than those that are slower. SSDs make virtually no noise at all, since they're non-mechanical.

Power: An SSD doesn't have to expend electricity spinning up a platter from a standstill. Consequently, none of the energy consumed by the SSD is wasted as friction or noise, rendering them more efficient. On a desktop or in a server, that will lead to a lower energy bill. On a laptop or tablet, you'll be able to eke out more minutes (or hours) of battery life.

Overall: Hard drives win on price, capacity, and availability. SSDs work best if speed, ruggedness, form factor, noise, or fragmentation (technically part of speed) are important factors to you. If it weren't for the price and capacity issues, SSDs would be the hands-down winner.

As far as longevity, while it is true that SSDs wear out over time (each cell in a flash memory bank can be written to and erased a limited number of times), thanks to TRIM command technology that dynamically optimizes these read/write cycles, you're more likely to discard the system for obsolescence (after six years or so) before you start running into read/write errors with an SSD. If you're really worried, there are several tools that monitor the S.M.A.R.T. status of your hard drive or SSD, and will let you know if you're approaching the drive's rated end of life. Hard drives will eventually wear out from constant use as well, since they use physical recording methods. Longevity is a wash when it's separated from travel and ruggedness concerns.


The Right Storage for You

So, does an SSD or HDD (or a hybrid of the two) fit your needs? Let's break it down:


• Enthusiast multimedia users and heavy downloaders: Video collectors need space, and you can only get to 4TB of space cheaply with hard drives.
• Budget buyers: Ditto. Plenty of cheap space. SSDs are too expensive for $500 PC buyers.
• Graphic arts and engineering professionals: Video and photo editors wear out storage by overuse. Replacing a 1TB hard drive will be cheaper than replacing a 500GB SSD.
• General users: General users are a toss-up. Folks who prefer to download their media files locally will still need a hard drive with more capacity. But if you mostly stream your music and videos online, then buying a smaller SSD for the same money will give you a better experience.


• Road warriors: People who shove their laptops into their bags indiscriminately will want the extra security of an SSD. That laptop may not be fully asleep when you violently shut it to catch your next flight. This also includes folks who work in the field, like utility workers and university researchers.
• Speed demons: If you need things done now, spend the extra bucks for quick boot-ups and app launches. Supplement with a storage SSD or hard drive if you need extra space (see below).
• Graphic arts and engineering professionals: Yes, we know we said they need hard drives, but the speed of an SSD may make the difference between completing two proposals for your client and completing five. These users are prime candidates for dual-drive systems (more on that below).
• Audio engineers and musicians: If you're recording music, you don't want the scratchy sound from a hard drive intruding. Go for quieter SSDs.

Hybrid Drives and Dual-Drive Systems

Back in the mid 2000s, some hard drive manufacturers, like Samsung and Seagate, theorized that if you add a few gigabytes of flash chips to a spinning hard drive, you'd get a so-called "hybrid" drive combining a hard drive's large storage capacity with the performance of an SSD, at a price only slightly higher than that of a typical hard drive. The flash memory acts as a buffer for frequently used files, so your system has the potential for booting and launching your most important apps faster, even though you can't directly install anything in that space yourself. In practice, hybrid drives work, but they are still more expensive and more complex than regular hard drives. They work best for people like road warriors who need both lots of storage and fast boot times. Since they're an in-between product, hybrid drives don't necessarily replace dedicated hard drives or SSDs.

In a dual-drive system, the system manufacturer will install a small SSD primary drive (C:) for the operating system and apps, and add a larger spinning hard drive (D: or E:) for storing files. This works well in theory; in practice, manufacturers can go too small on the SSD. Windows itself takes up a lot of space on the primary drive, and some apps can't be installed on other drives. Some capacities may also be too small. For example, you caninstall Windows on a SSD as small as 16GB, but there will be little room for anything else. In our opinion, 120GB to 128GB is a practical minimum size for the C: drive, with 256GB or more being even better. Space concerns are the same as with any multiple-drive system: You need physical space inside the PC chassis to hold two (or more) drives.

Last but not least, an SSD and a hard drive can be combined (like Voltron) on systems with technologies like Intel's Smart Response Technology (SRT). SRT uses the SSD invisibly to act as a cache to help the system more speedily boot and launch programs. As on a hybrid drive, the SSD is not directly accessible by the end user. SRT requires true SSDs, like those in 2.5-inch form factors, but those drives can be as small as 16GB in capacity and still boost performance; since the operating system isn't being installed to the SSD directly, you avoid the drive space problems of the dual-drive configuration mentioned above. On the other hand, your PC will need space for two drives, a requirement that may exclude some laptops and small-form-factor desktops. You'll also need the SSD and your system's motherboard to support the caching technology for this scenario to work. All in all, however, it's an interesting workaround.

The Storage of Tomorrow

It's unclear whether SSDs will totally replace traditional spinning hard drives, especially with shared cloud storage waiting in the wings. The price of SSDs is coming down, but they're still too expensive to totally replace the terabytes of data that some users have in their PCs and Macs. Cloud storage isn't free, either: You'll continue to pay as long as you want personal storage on the Internet. Local storage won't go away until we have ubiquitous wireless Internet everywhere, including in planes and out in the wilderness. Of course, by that time, there may be something better.

Info from https://www.pcmag.com/article2/0,2817,2404258,00.asp

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The Latest Updated: SFP Modules for Cisco Catalyst 2960-X Series Switches

January 12 2018 , Written by Cisco & Cisco Router, Network Switch Published on #Cisco Switches - Cisco Firewall, #Cisco & Cisco Network, #Cisco Modules & Cards, #Networking

We are so familiar with the hot Catalyst 2960-X series, and what are the SFP Transceiver Models for 2960 X Series? Check the table below about the latest SFP models for 2960 X Series.

Catalyst 2960 X Series

Network Device

Transceiver Model

Minimum Software Release Required

DOM Support

Software Release














SFP Transceivers

Model Number

Transceiver Description


1000BASE-T SFP transceiver module for Category 5 copper wire, RJ-45 connector


1000BASE-T SFP transceiver module for Category 5 copper wire, RJ-45 connector, Extended Temperature


1000BASE-SX SFP transceiver module for MMF, 850-nm wavelength, dual LC/PC connector


1000BASE-LX/LH SFP transceiver module for MMF and SMF, 1300-nm wavelength, dual LC/PC connector


1000BASE-ZX SFP transceiver module for SMF, 1550-nm wavelength, dual LC/PC connector


1000BASE-BX10 SFP module for single-strand SMF, 1490-nm TX/1310-nm RX wavelength, single LC/PC connector


1000BASE-BX10 SFP module for single-strand SMF, 1310-nm TX/1490-nm RX wavelength, single LC/PC connector


1000BASE-BX10 SFP module for single-strand SMF, 1550-nm TX/1310-nm RX wavelength, single LC/PC connector


1000BASE-BX10 SFP module for single-strand SMF, 1310-nm TX/1550-nm RX wavelength, single LC/PC connector


1000BASE-BX10 SFP module for single-strand SMF, 1570-nm TX/1490-nm RX wavelength, single LC/PC connector


1000BASE-BX10 SFP module for single-strand SMF, 1490-nm TX/1570-nm RX wavelength, single LC/PC connector


1000BASE-BX10 SFP module for single-strand SMF, 1490-nm TX/1310-nm RX wavelength, single LC/PC connector


Dual-channel 1000BASE-BX10 SFP module for single-strand SMF, 1490-nm TX/1310-nm RX wavelength, two single LC/PC connectors


1000BASE-SX SFP transceiver module for MMF, 850-nm wavelength, extended operating temperature range and DOM support, dual LC/PC connector


1000BASE-LX/LH SFP transceiver module for MMF and SMF, 1300-nm wavelength, extended operating temperature range and DOM support, dual LC/PC connector


1000BASE-EX SFP transceiver module for SMF, 1310-nm wavelength, extended operating temperature range and DOM support, dual LC/PC connector


1000BASE-ZX SFP transceiver module for SMF, 1550-nm wavelength, extended operating temperature range and DOM support, dual LC/PC connector


1000BASE-T SFP transceiver module for Category 5 copper wire, extended operating temperature range, RJ-45 connector


1000BASE-SX SFP transceiver module for MMF, 850-nm wavelength, industrial Ethernet, dual LC/PC connector


1000BASE-LX/LH SFP transceiver module for MMF and SMF, 1300-nm wavelength, industrial Ethernet, dual LC/PC connector


1000BASE-ZX SFP transceiver module for SMF, 1550-nm wavelength, industrial Ethernet, dual LC/PC connector


1000BASE-SX SFP transceiver module for MMF, 850-nm wavelength, extended operating temperature range and DOM support, dual LC/PC connector


1000BASE-LX/LH SFP transceiver module for MMF and SMF, 1300-nm wavelength, extended operating temperature range and DOM support, dual LC/PC connector


1000BASE-ZX SFP transceiver module for SMF, 1550-nm wavelength, dual LC/PC connector


Gigabit passive optical network (GPON) Class B+ SFP OLT transceiver module, 1490-nm TX/1310-nm RX wavelength


Gigabit passive optical network (GPON) Class B+ SFP OLT transceiver module, 1490-nm TX/1310-nm RX wavelength, industrial temperature range


Gigabit passive optical network (GPON) Class C+ SFP OLT transceiver module, 1490-nm TX/1310-nm RX wavelength


Gigabit passive optical network (GPON) Class C+ SFP OLT transceiver module, 1490-nm TX/1310-nm RX wavelength, industrial temperature range

1CPN 10-2624-01 or later only.

The full data sheet of Cisco Gigabit Ethernet Transceiver Modules Compatibility Matrix you can visit here:



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Wi-Fi/802.11x Standards

January 8 2018 , Written by Cisco & Cisco Router, Network Switch Published on #Networking, #IT, #Technology

Wi-Fi is so popular today. Do you know the Wi-Fi standards and how wifi works?

In the following part we will share the main information about the Wi-Fi standard (also called the 802.11x standard). The original info from


Wi-Fi is a term for certain types of wireless local area networks (WLAN) that use specifications in the 802.11 family--for example,  Wi-Fi Direct, a peer-to-peer specification that allows devices certified for Wi-Fi Direct to exchange data without an internet connection or a wireless router. 

Products that pass Wi-Fi Alliance tests for interoperability, security and application-specific protocols are labeled "Wi-Fi CERTIFIED," a registered trademark of the Alliance.

How does Wi-Fi work?

A Wi-Fi network uses radio waves to wirelessly transmit information across a LAN, the reach of which can be extended by a Wi-Fi range extender. A computer utilizes a wireless adapter to translate data transmitted by radio waves. These waves are different from those emitted by, for example, FM radios, for which frequency is measured in megahertz (MHz). Wi-Fi's signals are transmitted in frequencies of between 2.5 and 5 gigahertz (GHz). This signal is then transmitted from the adapter through a router, after which it is sent to the internet.

Wi-Fi is widely used in businesses, agencies, schools and homes as an alternative to a wired LAN. Many airports, hotels and fast-food facilities offer public access to Wi-Fi networks. These locations are known as hotspots. Many charge a daily or hourly rate for access, but some are free. An interconnected area of hotspots and network access points is known as a hot zone.

What are hotspots?

Modern smart phones and tablets are also able to turn into Wi-Fi hotspots, using their cellular network connections to provide wireless internet connectivity to computers and other devices.

To access Wi-Fi hotspots, computers should include wireless adapters. These can be found on laptops and mobile devices, such as tablets or mobile phones. If for some reason your computer doesn't include such an adapter, one can be purchased that can be inserted into the PCI slot or USB port. Your computer should then be able to locate Wi-Fi networks automatically in the area. These can either be open networks or protected networks; the latter can be joined by entering a Wi-Fi password.

Unless adequately protected, a Wi-Fi network can be susceptible to access by unauthorized users who use the access as a free internet connection. The activity of locating and exploiting security-exposed wireless LANs is called war driving. An identifying iconography, called war chalking, has evolved. Any entity that has a wireless LAN should use security safeguards, such as the Wired Equivalent Privacy, or WEP, encryption standard; the more recent Wi-Fi Protected Access, or WPA; Internet Protocol Security, or IPsec; or a virtual private network, or VPN. 

The term Wi-Fi was created by the Wi-Fi Alliance as a play on Hi-Fi, an abbreviation for high fidelity, which referred to high-quality audio reproduction. Similarly, Wi-Fi is often thought to be short for wireless fidelity. However, according to the Wi-Fi Alliance, Wi-Fi is not an abbreviation. The confusion may stem from the fact that the Alliance briefly used, "The standard for wireless fidelity," as a slogan for Wi-Fi. 

Originally, Wi-Fi certification was applicable only to products using the 802.11b standard.

Today, Wi-Fi can apply to products that use any 802.11 standard. The 802.11 specifications are part of an evolving set of wireless network standards known as the 802.11 family.

The particular specification under which a Wi-Fi network operates is called the "flavor" of the network.



Basics of physical and logical networking concepts



LAN/MAN bridging and management. Covers management and the lower sublayers of OSI Layer 2, including MAC-based bridging (Media Access Control), virtual LANs and port-based access control.


Logical Link

Commonly referred to as the LLC, or Logical Link Control specification. The LLC is the top sublayer in the data-link layer, OSI Layer 2. Interfaces with the network Layer 3.



"Granddaddy" of the 802 specifications. Provides asynchronous networking using "carrier sense, multiple access with collision detect" (CSMA/CD) over coax, twisted-pair copper and fiber media. Current speeds range from 10 Mbps to 10 Gbps. Click for a list of the hot 802.3 technologies.


Token bus



Token ring

The original token-passing standard for twisted-pair, shielded copper cables. Supports copper and fiber cabling from 4 Mbps to 100 Mbps. Often called "IBM Token-Ring."


Distributed queue dual bus (DQDB)

"Superseded **Revision of 802.1D-1990 edition (ISO/IEC 10038). 802.1D incorporates P802.1p and P802.12e. It also incorporates and supersedes published standards 802.1j and 802.6k. Superseded by 802.1D-2004." (See IEEE status page.)


Broadband LAN practices

Withdrawn standard. Withdrawn date: Feb. 7, 2003. No longer endorsed by the IEEE. (See IEEE status page.)


Fiber optic practices

Withdrawn PAR. Standards project no longer endorsed by the IEEE. (See IEEE status page.)


Integrated services LAN

Withdrawn PAR. Standards project no longer endorsed by the IEEE. (See IEEE status page.)


Interoperable LAN security

Superseded **Contains: IEEE Standard 802.10b-1992. (See IEEE status page.)



Wireless LAN Media Access Control and Physical Layer specification. 802.11a,b,g,etc. are amendments to the original 802.11 standard. Products that implement 802.11 standards must pass tests and are referred to as "Wi-Fi-certified."



  • Specifies a PHY that operates in the 5 GHz U-NII band in the U.S. -- initially 5.15-5.35 and 5.725-5.85 -- since expanded to additional frequencies;
  • Uses Orthogonal Frequency-Division Multiplexing;
  • Enhanced data speed to 54 Mbps; and
  • Ratified after 802.11b.



  • Enhancement to 802.11 that added higher data rate modes to the DSSS (Direct Sequence Spread Spectrum) already defined in the original 802.11 standard;
  • Boosted data speed to 11 Mbps;
  • 22 MHz bandwidth yields three nonoverlapping channels in the frequency range of 2.400 GHz to 2.4835 GHz; and
  • Beacons at 1 Mbps, falls back to 5.5, 2 or 1 Mbps from 11 Mbps max.



  • Enhancement to 802.11a and 802.11b that allows for global roaming; and
  • Particulars can be set at Media Access Control layer.



  • Enhancement to 802.11 that includes quality-of-service features; and
  • Facilitates prioritization of data, voice and video transmissions.



  • Extends the maximum data rate of WLAN devices that operate in the 2.4 GHz band, in a fashion that permits interoperation with 802.11b devices;
  • Uses OFDM Modulation (Orthogonal FDM); and
  • Operates at up to 54 (Mbps, with fallback speeds that include the "b" speeds.



  • Enhancement to 802.11a that resolves interference issues;
  • Dynamic frequency selection; and
  • Transmit power control.



  • Enhancement to 802.11 that offers additional security for WLAN applications; and
  • Defines more robust encryption, authentication and key exchange, as well as options for key caching and preauthentication.



  • Japanese regulatory extensions to 802.11a specification; and
  • Frequency range of 4.9 GHz to 5.0 GHz.



  • Radio resource measurements for networks using 802.11 family specifications



  • Maintenance of 802.11 family specifications; and
  • Corrections and amendments to existing documentation.



  • Higher-speed standards;
  • Several competing and noncompatible technologies -- often called "pre-n";
  • Top speeds claimed of 108, 240, and 350+ MHz; and
  • Competing proposals come from the groups, EWC, TGn Sync and WWiSE, and are all variations based on MIMO (multiple input, multiple output).



  • Misused generic term for 802.11 family specifications


Demand priority

Increases Ethernet data rate to 100 Mbps by controlling media utilization.


Not used

Not used


Cable modems

Withdrawn PAR. Standards project no longer endorsed by the IEEE.


Wireless personal area networks

Communications specification that was approved in early 2002 by the IEEE for wireless personal area networks, or WPANs.



Short range (10m) wireless technology for cordless mouse, keyboard and hands-free headset at 2.4 GHz.



Short-range, high-bandwidth ultra wideband link



Short-range wireless sensor networks


Mesh network

  • Extension of network coverage without increasing the transmit power or the receiver sensitivity;
  • Enhanced reliability via route redundancy; and
  • Easier network configuration and better device battery life.


Wireless metropolitan area networks

This family of standards covers Fixed and Mobile Broadband Wireless Access methods used to create wireless metropolitan area networks. Connects base stations to the internet using OFDM in unlicensed (900 MHz, 2.4, 5.8 GHz) or licensed (700 MHz, 2.5-3.6 GHz) frequency bands. Products that implement 802.16 standards can undergo WiMAX certification testing.


Resilient Packet Ring

IEEE working group description


Radio Regulatory TAG

IEEE 802.18 standards committee



IEEE 802.19 Coexistence Technical Advisory Group


Mobile Broadband Wireless Access

IEEE 802.20 mission and project scope


Media Independent Handoff

IEEE 802.21 mission and project scope


Wireless regional area network

IEEE 802.22 mission and project scope

History of Wifi

This was last updated in January 2017

Info from http://searchmobilecomputing.techtarget.com/definition/Wi-Fi


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