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Longevity of USB Flash and Wear Leveling

I think we have all heard a USB can only be used so many times.  Some say the number is 1,000 writes – some say the number is 100,000 writes.  One thing I do know for sure, it’s impossible to tell on any one specific device.  The life cycle of a USB is directly related to the flash memory…and from model to model or style to style, who knows what quality of flash is used.  With that said, we can still explain the theory behind making USB drives last longer.  For the most part it boils down to several elements  A)  the memory type and quality and B) the wear leveling technique.

As a quick summary the NAND flash in USB can be either SLC, MLC or TLC (single cell, multi-layer cell or triple-layer cell memory).  Typically you will find MLC and now mostly TLC in USB sticks.  SLC can be found but typically on the very high end devices.

Wear leveling is a technique to prolong the life of the erasable flash memory.  To summarize, flash memory has individual, erasable segments that can be set as zero’s or ones (set as either positive or negative charge).  However, after a certain number of erase and write cycles the segment (cell) becomes too unstable for reliable use.

Wear leveling is the algorithm used by the controller on the device which attempts to arrange the erase and writes evenly across the flash medium.  Typically flash can have a cycle between 3,000 and 5,000 erase/writes.  In addition to the usable area, the flash also has some cells with specific blocks for extended live which can handle up to 100,000 writes.  This is the area where the controller makes not of the segments previously used and maps out the next best cells to use during an erase/write cycle.

There are three types of wear leveling.

No wear leveling – A Flash memory storage system with no wear leveling will not last very long if it is writing data to the flash. Without wear leveling, the Flash controller must permanently assign the logical addresses from the host computer to the physical addresses of the Flash memory. This means that every write to a previously written block must first be read, erased, modified, and re-written to the same location. This is very time consuming and highly written locations will wear out quickly with other locations even being completely unused. Once a few blocks reach their end of life the drive is no longer operable.

Dynamic wear leveling – The first developed type of leveling is called dynamic wear leveling and it uses a map to linklogicl block addresses from the host to the physical Flash memory. Each time the host writes replacement data, the map is updated so the original physical block is marked as invalid data, and a new block is linked to that map entry. Each time a block of data is re-written to the Flash memory it is written to a new location.

Static wear leveling – The other type of wear leveling is called static wear leveling which also uses a map to link the block addresses to physical memory addresses. Static wear leveling works the same as dynamic wear leveling except the static blocks that do not change are periodically moved so that these low usage cells are able to be used by other data. This rotational effect of block addressing enables an SSD to operate until most of the blocks are near their end of life.

The above are three types of wear leveling and there are three types of techniques used to extend the life of a USB drive.

Error correction – Code which is kept and logs bad blocks so they cannot be used again in future writes.

Pool reserve – Where if a write fails to a block it can be re-routed to the pool of reserved blocks and written there.

Track usage  – Blocks on the media can be tracked in a least recently used queue of some sort. The data structures for the queue itself must be wear leveled as well as this queue information is constantly changing.

Source:  Wikipedia and Nexcopy Inc. duplicator manufacturer.

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Rip and Tear Gigabytes To Go

Burning CDs is slow and impractical when at a clients site.  In addition, who wants to leave behind their 16GB flash drive with a mix of personal and professional information?  With that said, we designed a small pack of drives we could tear and use when needed.  Since we travel and present files to clients this gives us an easy, inexpensive and creative way to leave files with the client.

The design lends itself to the old-school flyers you’d see around town for a local band playing at a pub or someone looking to offer odd-job services.  The physical form factor says it all…quick, easy, here-ya-go.


Each pack of four is recycled paper used as it’s chassis/case and COB memory and USB connector (Chip On Board) for the memory.  Each tab is perforated for easy tear and use functionality.

The designer Kurt Rampton of Bolt Group offers the drives in a couple different

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Flash Memory – Supply and Demand

In recent weeks the cost of flash memory has increased substantially.  The commodity product, is for the most part, a stable consumable with pricing that fluctuations in single digit percentages.  However, lately the prices have increased between 10-30%.  As with any product there are variables which contribute to price and the following information might help explain why flash memory is getting more expensive.

The two largest manufacturers of flash memory (NAND memory) are Samsung and Toshiba.  Together they account for about 70% of the world’s flash.  These companies produce a wide variety of flash memory models and the factories have various levels of quality for the output of their product.

Typically the high performance memory that gets the best test ratings is sold to large consumers like Apple, Nokia and Sony.  As the ratings for the speed of the memory drop, these variants get pushed into the low-end market segments, such as USB drives and inexpensive MP3 players and other promotional gadgets.

In Q3 2012 Toshiba made an announcement they will reduce world wide production by 30%.  Since this time, flash pricing has remained stable and has not decreased in cost.

With the on-going patent battles between Apple and Samsung the Cupertino based company made a decision

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Flash Memory Puts Mars Curiosity into Safe Mode


As with any good project, there should always be a back up plan.  The Curiosity for Mars is no different.  The system has a B-Side computer in the event the A-Side computer went down…well guess what, it went down.

There is a theory that cosmic rays affected some of the flash memory on Curiosity causing the A-Side computer to shut down and reboot into Safe Mode.

JPL is currently backup up the A-Side data to the B-Side computer and should reboot by weeks end.  Configuration and data transfer can take a while, then of course the verification process of everything done right.

JPL states:

“The hardware that we fly is radiation tolerant, but there’s a limit to how hardened it can be, you can still get high-energy particles that can cause the memory to be corrupted. It certainly is a possibility and that’s what we’re looking into.”

For updates please visit the NASA website.

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Dell USB Project Called Ophelia

If you haven’t heard,DELL is looking to buy back it’s public shares and go private.  Why you ask?  Going private would allow them to make quick and swift changes with in the company to re-invent itself.  Currently the never-ending demands of the stock holders and investors ties their hands in freedom to create as they wish.

DELL, so it is said, started a new code project call Ophelia.  The project is turning a USB key into a portable desktop.  The USB would have the ability to access online software tools and operating systems.  The USB solution from Ophelia will still require a hardware setup (someone’s PC) so think of it as a USB stick high-jacking the processor, RAM, motherboard, video controller etc to run it’s own OS.

We’ve seen things like this from smaller, start-up companies,  but DELL has the ability to really make this main stream.  The rumor on target price is $50 US Dollars.

I for one believe the ability to high-jack another PCs hardware doesn’t warrant it enough to be more then a complimentary tool to one’s main PC.  Now if DELL can high-jack the

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LaCie Porsche Design SSD USB 3.0 Hard Drive

Slim is in…hasn’t that been the motto of runway models for the past 20 years.  I guess you can say the same for tech gadgets, laptops and of course storage peripherals.

LaCie introduces the Porsche Designed ultra slim 120GB SSD hard drive.

The $149.99 Slim Drive P9223 by LaCie, powered by none other than USB 3.0, follows the same minimalist design set by Porsche Design. It has a thickness of a mere 11mm; this makes it a great compliment to a 17mm slim MacBook. It’s chassis is made of solid aluminum which doubles as a heat sink for fast dissipation of any heat build up from the NAND chips.

The LaCie Porsche SSD can top a transfer speed of 400/MBs.  But it’s not a walk in the park to get that data transfer rate.  You need to have a computer which supports the USB Attached SCSI [UAS] protocol.  This is a protocol which overcomes the aging bulk-only transport method which has been around since USB 1.0.

Source:  EverythingUSB.

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