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Topic: Wear levelling

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Flash memory

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	TrueCrypt Forums :: Implications of wear levelling for volumes on flash drives
		"Working at a slightly higher level than the device itself are various filesystem-level wear-levelling techniques which are used to decrease the number of erase operations which are necessary to update data, and the number of writes to a single segment of flash [[69]].
		Because of this type of operation it’s not possible to cycle fresh cells to reduce remanence effects without bypassing the filesystem, in fact the operation of the wear-levelling system acts to create a worst-case situation in which data is always written to fresh cells.
		This leads to the fact that writes are already a read/modify/erase/write process even before wear* levelling would require it*.
	forums.truecrypt.org /viewtopic.php?t=1702 (1570 words)

	Wear levelling - Wikipedia, the free encyclopedia
		Wear levelling (also written -levelling) is a technique for prolonging the service life of some kinds of eraseable computer storage media, e.g.
		Wear levelling involves arranging data so that erasures can be rotated evenly across the medium.
		On flash memory devices, this can be performed in hardware by a built-in microcontroller or in software by a special-purpose file systems such as JFFS or JFFS2.
	en.wikipedia.org /wiki/Wear_levelling (308 words)

	STMicroelectronics \| Wear Leveling in Single Level Cell NAND Flash Memories (Site not responding. Last check: 2007-10-09)
		Wear levelling is implemented in the Flash Translation Layer which is the additional software layer between the File System and the NAND Flash memory (see Figure 1.A).
		This vector is loaded into the RAM when the system boots and the Wear Leveling algorithm uses it to ensure the uniform use of the NAND Flash device by mapping the virtual blocks onto the youngest physical blocks.
		The Second Level Wear Leveling is triggered when the difference between the maximum and the minimum number of write cycles per block reaches a specific threshold.
	www.st.com /stonline/books/ascii/docs/10122.htm (1240 words)

	CompactFlash... (Site not responding. Last check: 2007-10-09)
		Explicite wear levelling is not performed, > but the net result is some degree of wear levelling.
		You have only 'accidental' wear levelling, using two blocks alone while leaving the 48 containing code entirely untouched.
		Of course that's a little contrived, we're assuming a block dies _on_ the 1 millionth erase and that there are no other bad blocks as you might expect on NAND.
	lists.infradead.org /pipermail/linux-mtd/2003-May/007726.html (242 words)

	Talik: Mine Levelling Rail (Site not responding. Last check: 2007-10-09)
		The Mine Levelling Rail is a unit composed of a carrier rail and replaceable wear parts.
		Once the Levelling Rail is mounted on the undercarriage of the scoop tram, it immediately begins levelling your roadways as the equipment works.
		The Levelling Rail is placed in such a way that it does not protrude outside the wheels of the vehicle and can never get hooked up, or put undesirable material into the roadway.
	www.mts.net /~talikman/minelevelling.html (169 words)

	RoSPA : Play Safety : Information Sheets : Loose Impact Attenuating Surfaces
		As the upper surface tends to wear, bark pieces of the lower layer will naturally become dislodged, to renew and maintain the surface layer.
		As LIAS have high impact absorbency resulting from the natural ability of the surface to “move” it is important to have readily available additional bark available to top up to the original level to ensure that the desired critical fall height rating is maintained.
		Heavy wear areas will need additional material to be raked in from the surrounding areas into any depressions usually on a monthly basis depending on use.
	www.rospa.com /playsafety/info/04_looseimpact.htm (748 words)

	[No title] (Site not responding. Last check: 2007-10-09)
		A: The jffs2 file system includes wear levelling to address the issues of lifetime on flash cells.
		The million write cycles will last approximately 10 years if you are doing an update every 5 minutes, assuming no wear levelling.
		Accounting for wear levelling, the flash will likely outlive the protocols on which it is based.
	alt.org /mbm/wrt54g/OpenWrt-FAQ.txt (662 words)

	Gameplanet - Reviews - Dynasty Warriors Advance
		Once you have yourself accustomed to this - a big hint is in the colours they wear - then it's all a matter of defeating whomever you need to defeat to make it through to the end.
		Levels are made up of two phases: a movement and a battle phase.
		After certain situations are met you will find your character levelling up, allowing him to wield weapons you have found scattered around the landscape, some of which are charged with different elements, allowing them to burn, electrocute or poison enemy squadrons.
	www.gameplanet.co.nz /mag.dyn/Reviews/2914.html (1632 words)

	Prophecy :: The Mud (Site not responding. Last check: 2007-10-09)
		If gains is not dependent on the eq you wear, then there will be no need to wear leveling eq and players will be able to wear their questeq at all times and that is a bad situation..
		Eventually, the persons prime stat would be maxed, and the secondary stats would rise (but the will never be as high as the prime stat), and if there are enough trains, the 3rd stats would rise(these being roughly in the same amount as the secondary stats, but slightly lower).
		Wis should be affected by experience or level, not age, to avoid people just afk botting to get their wis up.
	www.mud.lu /modules.php?op=modload&name=phpBB_14&file=index&action=viewtopic&topic=188&16 (2475 words)

	Ask OLPC a Question about Hardware - OLPCWiki
		If you get stuck, try JFFS as a keyword.
		Will wear levelling and bad block management be used to prevent and cope with failure of cells from excessive overwriting of some blocks of the 512mb flash drive?
		Built into JFFS2, as well as compression to reduce the data size.
	wiki.laptop.org /go/Ask_OLPC_a_Question_about_Hardware (3046 words)

	CIOL : Linux Features : Linux system development on an embedded device
		The Ext2 filesystem does not support wear levelling, thereby reducing sector/flash life.
		(Wear levelling ensures that different areas of the address range are used for writes and/or erases in rotation to extend flash life.)
		When a little amount of data needs to be changed, the Ext2 filesystem copies the whole sector to memory (DRAM), merges the new data in memory, and writes back the whole sector.
	www.ciol.com /content/search/showarticle.asp?arid=33638&pageNo=5 (775 words)

	Linux system development on an embedded device
		When choosing a kernel for a project, you need to evaluate how stable the latest release is, whether it caters to the project requirements and the hardware platform, the comfort level from a programming point of view, and other intangibles.
		At the lowest level are the screen and input device drivers (as for the keyboard or mouse) to interact with the actual hardware.
		At the uppermost level, Microwindows supports two APIs: the Win32/WinCE API implementation also known as Microwindows, and the other API mostly resembles that of GDK and is known as Nano-X. Nano-X is used on Linux.
	www-128.ibm.com /developerworks/library/l-embdev.html (6645 words)

	BetaNews \| Samsung Builds Flash Based Disk Drive (Site not responding. Last check: 2007-10-09)
		You have to understand that the internal memory controller of the hard drive takes into account wear leveling - we are not talking about raw flash memory cells, but about an integrated hard drive which uses flash memory.
		Wear Leveling extends the lifetime of NAND Flash devices because it ensures that even if an application writes to the same virtual blocks over and over again, the program/erase cycles will be distributed evenly over the NAND Flash memory.
		With wear leveling, you can achieve the stated lifetime of 50+ years.
	www.betanews.com /article/Samsung_Develops_FlashBased_Disk_Drive/1116953138 (1827 words)

	CompactFlash... (Site not responding. Last check: 2007-10-09)
		Personally I am not really bothered by the lack of wear levelling on some NAND systems.
		Explicite wear levelling is not performed, but the net result is some degree of wear levelling.
		My understanding is that full-size (PCMCIA) ATA cards support explicite wear levelling, but CF does not.
	lists.infradead.org /pipermail/linux-mtd/2003-May/007725.html (222 words)

	Big AND Flash memories write faster: News from Renesas Technology Europe
		The provision of on-chip memory management functions, such as bad-sector management, wear levelling and error correction, reduces the design workload by simplifying the system design.
		This allows the chip to achieve 100% perfect operation throughout its lifetime, regardless of whether a defect is present when the chip is shipped or occurs after shipment, enabling system design to be completed in a short period.
		The wear levelling function allows effective use of Flash memory rewrite areas and enables Flash life to be extended.
	www.electronicstalk.com /news/ren/ren125.html (605 words)

	Big Flash chips integrate memory management: News from Renesas Technology Europe
		The built-in memory-management functions, such as bad-sector management, wear levelling and error correction, have been optimised for on-chip use based on experience gained from the development of controllers for Flash cards such as CompactFlash and MultiMediaCards.
		In this way, the chip itself achieves 100% perfect operation throughout its lifetime, regardless of whether a defect is present when the chip is shipped or occurs after shipment, enabling system design to be completed in a short period.
		The wear levelling function enables effective use of Flash memory rewrite areas and extends Flash life.
	www.electronicstalk.com /news/ren/ren137.html (583 words)

	The Old New Thing : You probably don't want to run programs directly off your USB memory drive
		USB flash drives will actually do wear levelling which does greatly mitigate against the wear and tear - you won't constantly be doing erase cycles on the same flash block.
		In the case of embedded devices running off of flash that's soldered on board (cellphones are the prime example), the wear leveling is usually handled in software.
		And while we're on the subject of flash wearing out, I once attempted to use an old compactflash card to transfer data from an old Windows 95 laptop to a modern XP machine.
	blogs.msdn.com /oldnewthing/archive/2005/12/15/504089.aspx (4271 words)

	[Yaffs] [Yaffs-archive] Re: blkmtd (and YAFFS)
		If this is happening then extra wear levelling is not going to help.
		If that is indeed the case then some such wear levelling fs might help.
		The biggest problem I see is that YAFFS and JFFSx achieve their robustness by dealing with the flash directly and do not have logical to physical mapping layers.
	www.aleph1.co.uk /pipermail/yaffs/2004q2/000542.html (466 words)

	[Yaffs-archive] Fwd: Re: Inquiry About YAFFS
		However, the > way > that blocks are allocated and freed does cause some wear levelling to > happen.
		> I will be adding some explicite wear levelling in the future (maybe the > next > couple of weeks).
		The journalling strategy used in > YAFFS > means that there is no position awareness (ie the data does not have to > be in > a particular physical area of the NAND).
	www.aleph1.co.uk /pipermail/yaffs/2003q1/000343.html (1403 words)

	Wear leveling in USB memory sticks (flash drives)?
		Wear leveling in USB memory sticks (flash drives)?
		I'm talking about wear leveling in the firmware of the device.
		Yes that's a problem, if wear leveling is not available.
	www.howtofixcomputers.com /bb/ntopic4939.html (1758 words)

	2001 Linux Symposium: paper abstract
		Until recently, the common approach to using Flash technology in embedded devices has been to use a pseudo-filesystem on the flash chips to emulate a standard block device and provide wear levelling, and to use a normal filesystem on top of that emulated block device.
		JFFS is a log-structured filesystem designed by Axis Communications AB in Sweden specifically for use on flash devices in embedded systems, which is aware of the restrictions imposed by flash technology and which operates directly on the flash chips, thereby avoiding the inefficiency of having two journalling filesystems on top of each other.
		This presentation will give an overview of the restrictions imposed by flash technology and hence the design aims of JFFS, and the implementation of both JFFS and the improvements made in version 2, including compression and more efficient garbage collection.
	www.linuxsymposium.org /2001/abstracts/jffs.php (138 words)

	ST \| NAND Flash
		Wear levelling is implemented in the Flash Translation Layer which is the additional software layer between the File System and the NAND...
		STMicroelectronics Wear Leveling in Single Level Cell NAND Flash Memories
		The most common solution to connect multiple Single Level Cell NAND Flash devices to a microcontroller system bus is to connect them...
	www.st.com /site-index/NAND-Flash.htm (1498 words)

	JFFS : The Journalling Flash File System
		Until recently, the common approach to using Flash memory technology in embedded devices has been to use a pseudo-filesystem on the flash chips to emulate a standard block device and provide wear levelling, and to use a normal file system on top of that emulated block device.
		JFFS is a log-structured file system designed by Axis Communications AB in Sweden specifically for use on flash devices in embedded systems, which is aware of the restrictions imposed by flash technology and which operates directly on the flash chips, thereby avoiding the inefficiency of having two journalling file systems on top of each other.
		This paper will give an overview of the restrictions imposed by flash technology and hence the design aims of JFFS, and the implementation of both JFFS and the improvements made in version 2, including compression and more efficient garbage collection.
	sourceware.org /jffs2/jffs2-html (142 words)

	[No title] (Site not responding. Last check: 2007-10-09)
		If you only want the file-system to be writable while you're developing, but will ship the units read-only, it's acceptable to use the MTDBLOCK device, which performs writes by reading the entire erase block, erasing it, changing the range of bytes which were written to, and writes it back to the flash.
		This is used for truncating files, etc. Each node also has a 'version' number, which starts at 1 with the first node written in an file, and increases by one each time a new node is written for that file.
		Neither was wear levelling the physical medium that the data was stored on (hard disk platters have a significantly more read/write life than flash chips).
	ftp.linux.org.uk /pub/people/dwmw2/mtd/cvs/mtd/mtd-jffs-HOWTO.txt (8592 words)

	Renesas Technology's superAND Flash Memory Driver Software Gains Symbian OS Compliance; Renesas Technology Joins ... (Site not responding. Last check: 2007-10-09)
		Renesas Technology's superAND flash memory is a leading device in the industry to built-in the error correction feature (Note 1), the wear leveling feature (Note 2) and the sector management function (Note 3), so generally the superAND flash memory reduces a system design load.
		The wear levelling feature is a function to even out the number of rewrites.
		As a chip becomes susceptible to damage if write operations are concentrated locally, when rewrite operation reaches a predetermined number of times, data and addresses are automatically switched to an area in which few rewrites have been performed.
	www.tmcnet.com /scripts/print-page.aspx?PagePrint=http://www.tmcnet.com/usubmit/2005/jan/1109064.htm (657 words)

	Smallest hard drive ever.
		Solid state's out considering how fast they wear down and optical doesn't even come close to magnetic storage in terms of bits per gram.
		Ferromagnetics platters, however, are not so easily damaged by wear.
		Unless it has some sort of wear leveling (http://en.wikipedia.org/wiki/Wear_levelling) engaged, it's going to wear down rather quickly.
	digg.com /technology/Smallest_hard_drive_ever. (1006 words)

	AVS Forums Archives - Driveless HTPC - Ram Drive (Site not responding. Last check: 2007-10-09)
		You'll need to disable disk swapping or you'll wear out your CF in no time.
		It should be able to be kept where it is going to be used.
		CF / Zip / Jaz / SDRam are the right ideas, but all have their potential drawbacks (slow, "wears out", non-bootable or volatile are some words that come to mind with these).
	archive.avsforum.com /avs-vb/history/topic/109868-1.html (3764 words)

	Leading Edge - Europe - 1/7/1999 - EDN (Site not responding. Last check: 2007-10-09)
		It communicates with modem and transceiver ICs via a Utopia Level 2 interface, distributing and collecting data to and from a range of service interfaces.
		Overall data rates can be greater than 155 Mbps downstream and 100 Mbps upstream, so you can design for physical media, such as asymmetric digital subscriber line, very-high-bit-rate digital-subscriber line, fibre to the home (or to the kerb), and hybrid-fibre coax.
		Internally, the TrueFFS flash-file system handles flash and incorporates wear levelling, bad-block marking and remapping, and full read/write.
	www.edn.com /article/CA56641.html (1826 words)

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