What Is Flash Memory?
Everyone talks about flash, but not too many users actually know how it works. Flash is a transistor-based silicon memory technology that can store information permanently by trapping electrons into so-called floating-gate transistors. Depending on the threshold voltage of the flash cell, the transistor will either remain insulated or become conductive. SLC flash (single-level cell) has only one voltage level, while MLC (multi-level cell) flash memory is capable of storing multiple bits per cell. Flash transistors become worn out with use and typically offer anywhere between 10,000 and a few million write cycles. Many flash products incorporate wear-levelling algorithms, which ensure all cells are worn evenly to maximize the lifespan of the product. The downside can be somewhat erratic performance.
There are two flash memory technologies: NOR and NAND, where NOR represents a "joint denial." This means that high (1) output only results if the two inputs, called the control gate and the floating gate, are low (0). If either one or both are high (1), no current will flow. With SLC flash, the stored data is reconstructed by detecting whether or not a current flows through the transistor. In case of MLC, the amount of current is used to determine the precise charge level of the floating gate. NOR flash can be fully addressed via an external bus for read operations, but shows rather slow write and erase times, because writing and erasing have to be performed block-wise. Also, NOR does not have any bad block management - this has to be taken care of by the host system. NOR is the ideal flash technology for non-volatile, long-term storage such as for firmware or BIOS applications.
Unlike NOR, NAND allows for a current flow if one of the inputs are high (1). NAND flash cannot be addressed cell by cell, but has to be read or written very much like hard drives; erasure only works block by block. Hence, a controller is required to access NAND flash properly, which typically also takes care of bad block management. NAND is used for memory cards and consumer devices and thanks to the controller, which is required in any case, manufacturers can easily optimize their production output for consumer products by marking existing bad blocks and by designating a large number of spare blocks. As a result, a 4-GB flash memory device will typically have at least several hundred megabytes of spare memory to equate bad blocks that may turn up over time. NAND’s operation is thus more efficient, as increased data densities allow for better utilization of the production output at existing capacity points. This is because more cells can be used as spares. Even if a device has bad blocks, the user will never know.
Flash Everywhere
Flash-based memory and storage products can be found in almost all market segments. While flash memory was first used to store firmware or BIOS information, it is increasingly used for such applications as flexible storage (think of portable USB flash sticks), temporary storage in such devices as a USB flash memory unit to boost the main memory of Windows Vista (ReadyBoost) and even for permanent storage. On the one hand, flash memory is starting to become physically integrated with hard drives, turning them into so-called Hybrid Hard Drives (H-HDDs). Hybrids are conventional hard drives with rotating platters, but they also have between 128 MB and a few gigabytes of flash memory to enable the operating system to utilize it both as permanent storage and as cache memory. This allows the drive’s spindle motor to come to a halt. Finally, flash is making inroads in the traditional hard drive space as well. For example, 1.8" and 2.5" flash-only hard drives have been around for several months, but low capacities or high costs have prevented it from penetrating anything except for the very high-end market (Bitmicro has a significant share in this sector). As the dollar-per-bit ratio continues to decrease, the future for flash SSDs is bright, indeed. Almost all memory vendors are getting ready to offer devices with 6- and 32-GB capacities, and it is only a matter of time until 64-GB and 128-GB devices become affordable.
Latest Internal Storage News
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- 24/01 – Best SSDs For The Money: January 2012
Congratulations - according to the article SSDs are also power generators because their power requirements are 30-400% below the energy consumption of traditional 2.5" hard drives. If an SSD consumed nothing it would be 100% less than some HDs.
Excellent stuff and this is only the first release.
What we needs is OS's and applications that can take advantage of the specific benefits of each memory device. I would want to store my OS and applications on a pair of these for lightning load times and have a drive for the data files and windows cache and system files that change.
The problem with the windows operating systems seems to be the huge ammount of disk activity and swapping of data that always seems to be going on even when you lots of memory.
Somewhere in April 2007 I talk sandisk in providing me with a 25" 32 Mb SSD disk to hold a experiment upgrading older PC's.
Allthough we had to pay approximately € 350,- (and that was with a good discount as I agreed to share the results with SanDisk) SanDisk provided us with the drive and I have it running in a older 2.4 Ghz Intel based HP330D PC since approx. June 2007.
My idea was that since graphic and CAD programs are paging heavily to disk when handeling bigger files (Autocad is doing this anyway) one could speed up this process by using a SSD since the transfer rates to disk are much much faster.
By upgrading the older PC's with a SSD we could avoid replacing those older PC's and keep them runnin for a other 2 years.
basically saving 50% on the hardware budget for the coming two years.
Just before I tried the SSD I bought two new HP xw4400 machines @ € 1740 each, just so you know what the difference in budget is).
I thought that thee size of the SSD (32Gb) would
not be a problem as data is kept on the server, one only needs space for the OS and programs.
This proved not completely to be true as when I wanted to install the new Adobe CS3 suite, (a shocking 15 Gb on disk, I could only install the parts that I needed from the CS3 (I didn't calculate with that CS3 update).
This problem however would not have occured when I would have gone for the 64Gb version of the SSD (And as announced by SanDisk, 128 Gb versions would be available soon)
So I started the experiment with the SSD, installed it on the SATA and did a clean install of OS and all programs.
And ........
....WITH SOME AMAZING RESULTS.......
Where I used to have the routine:
"turn on my PC in the morning and go and make a cup of coffee while waiting to log in to the server"
.....this is no more (I might have cut myself seriously in my fingers there)
The start-up time is simular (if not faster then)
the brand new HP xw4400's(OS WinXP pro 64bit) and my coffee will have to wait till I checked mail etc.
Running Autocad, Adobe CS3 or 3DSVIZ with seriously big files is not a problem anymore the paging out to disk is not noticable while working.
The small size of the disk does has some influance here as one have to leave 10Gb free for the swap files (that's the reason why I couldn't install the Adobe CS3, So if anyone wants to do the same go for the 64Gb SSD, and remember the Data has to be kept externally from the workstation, or put a big second HDD in).
There is also a big advantage in the disk maintenance as the SSD doesn't slow down due to defragmentation where this is seriously noticable with HDD's
I did run a PCmark05 (gained about 300 points)
however this doesn't measure the user experience
specifically on the issue of working with programs that page out to disk. Here I only can give you my user experience and that gained about 500%
I did ask support from SanDisk in properly measuring the gained speed and offered to share
all results but that is where I feel a bit let down by SanDisk as they didn't even respond to my proposal to assist me in measuring.
If you would ask me if I would buy a SanDisk SSD again to do the same, my answer is definitly...
.... YES .... but then at least 64Gb
I have three 64Gb SSD on my whishlist to upgrade
the remaining HPDX330D's.
I will not do it with the 5 older compaq machines,
(I find them major hardware trouble stations, burning out MoBo's and graphics, etc.) and the rising demand in hardware requirments of the software doesn't justify upgrading them with SSD's
I'll replace them with HP xw4400's (two each time)
However my priority at the moment is to get the network under CAT6 and Gigabyte ready as I think I can reach the most speed gain there for everyone. (can not figure out if to buy this bloody expensive 3com 48 port (€ 2500 ??) switch or the mor DIY netgear 24 port gigabyte switch( only € 700 ?)
Nico Ketel
Stephen Carr Architects
Ireland
nico@scarchitects.ie
http://www.scarchitects.ie
Special quote:
It is a hard world out there for the NOT it-specialist in smaller company's who get the responsibility over the company's hardware policy. ))))
uhhhh...... that should be 2.5" SSD at the start........ I would know where and how to fit a 25 inch one.........
maybe an other brilliant Idea building a 25" should hold a 10000 TeraByte (what would that be called anyway )))))
One other addition to my experience:
At home I recently tried a raptor (YEAH, YEAH GAMING, I admit) but even that delay's on the access time, now I didn't really compare the SSD with the raptor however I feel it is fair to say that:
When comparing mechanical drives to solid state drives the solid state drive will always win based on the acces time of the disk.
That's the core of the problem I tried to solve.
And I think I've proofed that with a practical field test over the past few months in the office.