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The ASUS solid-state NAND flash drive
The first mass produced notebook with flash memory as a primary storage device takes its first steps

This article was first posted on SiliconMadness.com

It's been the fear of tech forums everywhere, solid state storage failure.  Commercial grade flash memory chips typically have a threshold of 100,000 write/erase cycles per block, after which it could become unusable due to an increased error count while reading. This is a mean value, some fail after, some before. Reads also take a toll on that value, but they are almost negligible when compared to an erase cycle.

This has raised the question as to whether or not NAND is "ready" for high write operations.  Is flash memory reliable enough to replace magnetic media? 

The ASUS Eee PC is the first multi-purpose computing device available en masse that employs storage based solely on Flash memory, commonly known as a solid state drive (SSD). Being a pioneer, it will be an excellent test subject and a testimonial to the durability of flash based drives for use as an HDD replacement. Other flash based devices don't have the same kind of usage patterns and therefore aren't good for this purpose.

Since the Eee PC was released in November, one would think it is still quite early to expect some relevant data, but turns out that isn't true. Some users have already reported unusual behavior from their drives; some claim the main volume sizes have shrunk by as much as 500MB.  All cases revolve around Eee PCs that feature SLC Hynix HY27UG088G NAND chips.

Hynix advertises that its memory performs wear-leveling on-chip -- a technique used to even out memory cell usage so the flash memory does not write particular cells more than others.  Typically, if bad blocks are detected in this wear leveling, they are removed from the address table, resulting in fewer blocks in the drive volume. 

ASUS seems confident the isolated reports are not systemic.  ASUS spokesman Randy Chang tells DailyTech that the defect rate for the solid state storage devices on the Eee are lower than that of similar devices with traditional rotational media.  In addition, Chang assures us that any defective SSD problems, including shrinking volume sizes, are covered by ASUS warantee. 

Indeed, a quick search on the ASUS forums details only a handful of new posts about defective drives. 

Current 8GB Eee models use Mini PCI-Express SSD cards instead of onboard chips.  These can be removed and replaced by ASUS staff quickly if the drive fails.  ASUS would not comment about why it chose to not solder its storage directly onto the motherboard, saving precious space, but a clever forum poster points out that its easier to replace defective solid-state memory when its in in a PCIe adaptor.

One thing is clear though, with ASUS pledging to sell nearly four million Eees this year, the company is fairly confident in the ability of NAND memory and high write scenarios.  Apple and Lenovo both pledge to sell millions more NAND-based notebooks this year too: the Airbook and X300. 


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That's frightening
By therealnickdanger on 3/3/2008 9:52:58 PM , Rating: 2
I've always been a big supporter of flash-based storage, to the point of denying some of the realities of wear-leveling, I admit. I know that wear-leveling should normally not cause problems for years of use, but it never occurred to me that the controller would erroneously deactivate chunks of the storage. Would your data thus only be readable (hence, recoverable) or would it be gone forever?




RE: That's frightening
By das mod on 3/3/2008 11:39:54 PM , Rating: 2
what kind of relevant data can one possible have in a device such as this one ??? drive dies, data gone ... no biggie


RE: That's frightening
By taropie on 3/4/2008 3:28:43 AM , Rating: 2
True, in fact thats what the SDHC slot was meant for.


RE: That's frightening
By therealnickdanger on 3/4/2008 8:58:28 AM , Rating: 2
I agree that anyone that places all his proverbial eggs into one basket deserves to lose it all, but the target market of this device I would expect not to be able to afford a backup server or to even be very knowledgeable about SD expansion.


RE: That's frightening
By idconstruct on 3/4/2008 9:33:20 AM , Rating: 2
The 'chunks' of storage are very small... and it doesn't just delete your data... When it senses that its going bad, it just removes it from the 'pool'. Considering that the 'erase' function takes the biggest toll, it would seem to imply that the data isn't needed anyways.


RE: That's frightening
By MozeeToby on 3/4/2008 3:34:34 PM , Rating: 2
Not sure if I understand what you are saying so correct me if I'm wrong. You seem to imply that since erase is the biggest toll, the sectors that are failing are being erased frequently.

In reality, flash memory is "erased" every time a sector is written (ussually refered to as "flashed", hence the name). So if I change a single character in a file, the entire sector that that file is in gets erased and re-written.


Post-mortem, not post-moderm
By noirsoft on 3/3/2008 9:37:31 PM , Rating: 2
please correct.




RE: Post-mortem, not post-moderm
By Visual on 3/4/2008 7:58:33 AM , Rating: 2
The guy has a valid point, no need to downrate him.

And the title is still incorrect at the time of me posting this: it says post-morterm, should be post-mortem


Minor Problem
By Quiescent on 3/4/2008 8:55:35 AM , Rating: 2
I have been keeping an eye out on the eeeuser forum. (I do own a 4G Surf)

These problems are few and rare. Mostly associated with the already known 8G problem (Asus has stopped making them because there is something wrong with the PCI-E 8GB SSD card).

I can personally say that I haven't disabled swap on my nLited XP install and do use a lot of read/writes. But I never experienced any missing space. Now I do manage to experience a tight squeeze of space, because I am a power user.

I personally believe that if anybody experiences these problems it is because of hardware defects, which in that case, you'll want to send it their way if it's still under warranty.




Flash NAND Failure
By netgod on 3/5/2008 12:35:53 PM , Rating: 2
Correct me if I am wrong, but "failure" in flash terms is the decrease in write speed below acceptable norms. Rarely do you ever lose the data that is stored on failed flash, it simply takes much longer to Read/Write it. The way flash works, as I understand it, is that every time you Write/Erase flash, the speed of that flash decreases, until you reach a failure point.




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