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Fusion-io's CEO David Flynn - talks SSD - with

Editor:- July 23, 2010 - I've been speaking to Fusion-io since May 2007 - and I thought I already knew a lot about the company.

But I was pleasantly surprised to learn a lot of new things - in a talk I had with their CEO David Flynn, yesterday - which you might be interested to learn about too.
from SSD news

Fusion-io decouples storage software from 30 years of data spin
Editor:- Fusion-io recently released what it calls a "Virtual Storage Layer" which provides a set of enhanced programmatic interfaces for optimizing operations which use its ioMemory family of SSDs.

I had a briefing with Fusion-io's CEO David Flynn ostensibly to fill me in on more details about the new software tools - but as you can imagine - once we started talking about what's happening in the SSD market - and what we think might happen - we covered a wide range of topics - enough to fill several future articles.

The thinking behind the VSL is to provide software tools which enable developers to communicate in the new language of directly accessible flash SSD memory in a way which breaks away from the cumbersome restrictions and limitations of 30 year old software models which are layered on legacy hard disk sectors.

One obvious advantage of this method is performance. By using the VSL programmers have direct access to the large block writes and random reads which are characteristic of native flash storage. This visibility eliminates the risk - which can arise when working via an artificial HDD based I/O software model - that arms-length software can sometimes result in worsening the performance with an SSD instead of improving it.

The new SSD API can also enable developers to surgically remove operations which were originally created to ensure good operation with HDDs but which you don't need to do with Fusion-io's flash drives.

David Flynn cited an example of a write process in MySQL - in which 2 successive writes take place - as a defensive mechanism to ensure that data has been written to the hard drive and doesn't get lost if the power goes down.

The 2nd write isn't needed (as an integrity operation) for their flash SSD - because it will guarantee the data is written even if the power supply suddenly turns off. In fact doing the 2nd identical write to the same flash block could in most flash SSDs delay the next microscopic database operation.

The benefit of giving programmers an alternative programming model - is that functions like this - which were originally developed for rotating disk storage - can be removed or modified.

Therefore performance improvements can accrue not just from accelerating the same old operations faster - but by rewriting kernel code to improve its data form factor fit with the new nature of flash memory.

Reliability is a subject which we spoke a lot about - and I'll return to some of what we discussed in future articles.

Most flash SSD designs today were designed to interface through a traditional disk storage interface - like FC, SATA or SAS. That means they have an internal controller which translates the host I/O requests which come through the "disk" interface and translate these into block R/W requests for the flash memory - as well as doing a lot of other house-keeping functions as we've discussed in these pages before.

Most of the microprocessors (with a few rare exceptions) which are used as SSD controllers don't have end to end data integrity checks built into the datapaths of the CPU itself. Consequently they are vulnerable to cosmic radiation events which can destroy the integrity of the remapping tables and make the data unrecoverable.

David said that in his past career experience working in supercomputer environments - with big hard disk populations - those statistically rare events could cause systems to crash on a daily basis - making it necessary to investigate the weak design points of every single type of device in those networks until the culprits could be found and modified or changed.

The same risk exists in large SSD arrays.

Partly for this reason he said Fusion-io's product architecture doesn't include a processor on the PCIe card to perform the remapping functions. Instead remapping is done by the server host (and server makers have learned from painful experience to make sure their datapaths are end to end corrected.) David said there's a virtuous triangle which comes from this approach. Removing the need for a separate SSD controller reduces hardware count, and reduces cost while increasing reliability and increasing performance.

You need a fast enough multi-core host processor to handle this task- but then that's why you're using this type of SSD in the 1st place - because you have CPU performance which wants to get to work on the data.

Fusion-io's VSL supports Linux, Windows 64, FreeBSD, Solaris and VMware.

Even before talking to David I could see that if developers started writing applets to tweak the speed and reliability features of Fusion-io's SSDs - that would make users reluctant to look at any of the 100 or so other PCIe SSD companies which could be in the market next year.
pcie  SSDs - click to read article David agreed that customer stickiness of this type would not be something he would be unhappy about.
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Here's a sprinkling of the topics discussed when Fusion-io's CEO - David Flynn spoke to the mouse site.
Flash SSD storage density
It's well known that people have turned to SSDs for server acceleration because CPU clock rates stopped accelerating and hard disk spin rates stalled - but David Flynn suprised me by saying that in his view the DRAM market had run out of steam too.

At the chip level the storage capacity of flash is much denser than DRAM.

But because of the lower power consumption of flash you can pack much more flash into a rackmount SSD than the chip density comparisons would suggest.

He said that using today's technology you can get 200x more capacity using flash than RAM in a rackmount system. He said that petabyte SSD installations are technically feasible now.
the data driven economy
David Flynn said that in the near future datacenters would be regarded as drivers of the knowledge economy in the same way as factories were in the industrial age.
flaky SSDs and flash burnout in RAID
David Flynn said the situation regarding the misapplication of consumer grade SSD technology to enterprise applications was a real problem for the reputation of the SSD market.

He said one organization (which he named) had installed RAID systems using Intel SSDs in a high performance environment.

About half the SSDs had "burned out" after a year.

Worse than that - when the customer investigated more closely they found that some SSDs had failed in a way which had not been detected by the RAID controllers.

That meant the data was trashed.

David Flynn wryly commented that there was a lot more to marketing enterprise SSDs than adding an "e" to a consumer technology SSD brand (and redesignating it an "enterprise" product).

He said Intel has a very strong brand in the computer market and he doubted it would be dented - even by as many as 4 SSD design recalls - but customer education about SSDs is a serious issue in the industry.
weakness in some competing PCIe SSD architectures / the SSD Heresies
David Flynn shared his views about other oems - rushing to get into the PCIe SSD market.

Some products had been little more than cards which had a RAID controller and bunch of SATA SSDs repackaged on a card. (For example OCZ's Z-Drive - unveiled at CeBIT in March 2009.)

He said not only was performance terrible - because they were doing all that hard disk interface "rubbish" between the PCIe bus and the flash memory - but the products did not have end to end error correction. Any big installed base of such SSDs ran serious risks of uncorrectable random data corruption.

He said Fusion-io's attention to the subject of data integrity was one of the things which was appreciated and well understood by their server oem partners HP and IBM.

He said that some other new companies coming into the PCIe SSD market with native PCIe designs - such as LSI (working with Seagate) might find it difficult to solve subtle reliability problems - because the different parts and technologies (which include controllers from SandForce) would be coming from 4 (or more) different places.
storage reliability
David Flynn talked more about this subject than anything else.

Mostly it was related to SSDs and is reported elsewhere on this page.

But he also said that it was a bigger problem for hard disk based systems than most users fully appreciated - because of inadequate strength error correction designed into industry standard hard disk interfaces.

He said the only practical way to prevent data corruption in HDD based datacenters was to overlay additional levels of error checking and data healing outside the arrays. This harmed performance - but was essential.

He observed that many mid range RAID vendors approach big end user sites hoping to dislodge vendors like EMC with lower cost storage. But one of the added values in these big iron storage systems is the enterprise wide data integrity cushion which mid scale vendors can't easily penetrate or replicate.
hardware minimalism
David Flynn talked about the virtues of stripping out layers of unnecesary junk in the design of their SSD - which would only be there to emulate hard disk protocols.

He said this was one of the aspects of the company which had appealed to Steve Wozniak - who is now Fusion-io's Chief Scientist.

Flynn related one of the many legendary tales told about Wozniak's design of the Apple Computer - the world's first high volume desktop PC - when Wozniak replaced a whole bunch of chips which traditionally would have been needed to interface to a floppy drive - and instead used sofware.

Not only did that save cost - but by using the 6502 processor to calculate the momentun of the mechanics - his design gave better performance with the same floppy media than the dumb floppy chips it replaced.
"One petabyte of enterprise SSD could replace 10 to 50 petabytes of raw HDD storage in the enterprise - while also enabling all the apps to run faster."
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