Comments on: Flash futures

By: Amyl Ahola

Amyl Ahola — Tue, 18 Mar 2008 22:27:57 +0000

Your blog of March 11 on the future of flash technology is right on….as far as it goes. While you identify write performance as a concern, write endurance and especially flash read and program disturb phenomena are of equal or greater concern for high performance, high duty cycle enterprise applications.
Traditional approaches do not adequately address these concerns and result in performance expectations not being met together with a high risk of read and program disturbs turning into uncorrectable errors. I believe new, non-traditional, controller architecture approaches (such as Pliant’s) will be developed providing solutions to these concerns resulting in even higher performance SSD’s without adding significant cost over existing controllers.
The future of SSD IS becoming clear. When these advanced controllers / SSD’s become available later this year it is expected the acceptance of SSD in the enterprise market will be greatly accelerated. I expect to see broad adoption in the enterprise during 2009.

By: christopher

christopher — Sat, 15 Mar 2008 05:17:25 +0000

i have read the chip data sheets and written software to deal with NAND and NOR flash chips.

typical NAND flash parts do not require re-writing an entire block as a unit. that’s the unit of erasure, but only that.

there are some poorly design ftl’s that erase and re-write entire blocks at a time, but they are just that — poorly designed.

typical NAND flash parts only require that pages in a block be programmed sequentially. pages do not need to be programmed simultaneously.

this sequential page programming rqeuirement is trivial for a log structured store.

what’s more many SLC parts support partial page writes — a single page can be partionioned and programmed multiple times, typically up to four times.

By: e2eiod

e2eiod — Fri, 14 Mar 2008 05:50:14 +0000

E2EIoD stands for End-2-End Information on Demand.
My name is Robert Pearson. I have no claim to fame. Just a few good ideas.
I have a 256 MB flash drive I purchased in 2003 for ~$80 and was glad to get it.
Since 2003 I have used this drive for storing personal Information. I have never filled it up. Nor do I plan to test it by writing it full and deleting it all to test how long it will last. In addition, I now own 2 ea. 1 GB, and 1 ea. 2 GB flash drives. All purchased for much less than $80 ea. I have purchase plans for an 8 GB for $35.
I can replicate my entire Personal Computing world with 3 flash drives. One for the OS, one for the Information Storage and one for the Portable Apps. This is done for convenient management. Same way I do my disk drives. I have been working on making this Portable Computing Environment Plug-n-Play (PCE-PnP). Think in terms of what is required when the Stored Information URL is changed for whatever reason. EMC promised “soft-links” at the 1999 Phoenix Tech Conference. That would be nice.
What’s my point?
What’s all the fuss about?
The PCE Plug-n-Play would be a lot easier if flash were re-designed from the original design goals of “photo albums online” and replacements for “rotating rust” to take advantage of their true capability.
It may take a while before they are ready for the Enterprise. SCSI has come a long way to SAS and IDE to SATA. Remember the short-comings of SCSI?
Having an I/O map of your IT shop is a good thing for deciding where the “writes” and “reads” are. Today it would be good to add I/O by Content. In particular for your “defined” Information Stack (IS).
I work mostly with Information Retrieval using a vaporware SFO (Search, FInd, Obtain) function. This is 100% “reads”. If I have an area that is “write” intensive”, I have no problem leaving a SAS/SATA solution in place. Flash adds more value in other uses.

I’m surprised by the blank looks I get when I ask people what their Storage desires are? Then I ask what their Information Stack (IS) process looks like? Then I ask them if they have a Design-2-Implementation-2-Management picture or roadmap of this?
It is fairly easy to set up a matrix where you can compare your Information Stack needs, your Storage desires and how a particular Unit of Technology meets these.
This is unique to each IT shop. This is an easy way to see if flash would help.

Robin, I applaud your continuing commentary on the lack of “Lower Metric” responsibility by vendors.

By: Robin Harris

Robin Harris — Thu, 13 Mar 2008 10:12:45 +0000

Christopher,

While it is true that flash can read and write single pages, most flash chips write a single page by re-writing an entire block. IIRC some chips have a limited – like 3 single page – write limit without a block rewrite. However that technique works it doesn’t seem to have caught on.

Check out the chip data sheets for more info or StorageMojo’s SSD coverage.

Robin

By: Flash: the devil is in the details « Storage Effect

Flash: the devil is in the details « Storage Effect — Wed, 12 Mar 2008 14:31:10 +0000

[...] Robin Harris posted yesterday and last week on flash – both are interesting reading. My takeaway is that the more flash is applied, the more real-world wrinkles bubble up to the surface. That’s exactly as it should be – new technology buzz always begins with what’s possible, then moves to “OK, now how exactly will that work in my solution today?” [...]

By: christopher

christopher — Wed, 12 Mar 2008 01:03:51 +0000

That’s not quite right. With NAND Flash you erase blocks (sometimes called sectors) but you read and write pages. A typical part may have 64 pages per block.

See Figure 4 of Micron Tech Note 29-19 (http://download.micron.com/pdf/technotes/nand/tn2919.pdf) for an excellent visual explanation.