Samsung defends flash reliability in solid-state drives

Samsung is touting the reliability of solid-state drives, while citing an explosive market for the devices in server computers.

SSDs are based on flash memory chip technology and have no moving parts. Hard-disk drives (HDDs), in contrast, use read-write heads that hover over spinning platters to access and record data. With no moving parts, SSDs avoid both the risk of mechanical failure and the mechanical delays of HDDs. Therefore, SSDs are generally faster and more reliable. The catch is the cost: SSDs are currently much more expensive than HDDs.

Samsung 1.8-inch SSD

(Credit: Samsung)

There are also concerns about wear. That is, flash has the potential to wear out after tens (or hundreds) of thousands of write cycles.

This characterization, however, is too simplistic, according to Michael Yang, flash marketing manager at Samsung. A flash device that is rated at 100,000 write cycles, for example, can write 100,000 times "to every single (memory) cell within the device," Yang said. In other words, the device doesn't write to the same cell over and over again but spreads out the writes over many different cells. This is achieved through "wear leveling," which is carried out by the SSD's controller, he said.

This would make it virtually impossible to wear out a flash chip. Yang said a pattern could be perpetually repeated in which a 64GB SSD is completely filled with data, erased, filled again, then erased again every hour of every day for years, and the user still wouldn't reach the theoretical write limit. He added that if a failure ever does occur, it will not occur in the flash chip itself but in the controller.

On another topic, Yang cited explosive demand in the enterprise server market that caught his company by surprise. "At first it just sounded like an interesting idea," he said. But then demand took off. As Yang explained, companies like Citibank and American Express peg server performance on IOPS or input/output operations per second. "HDDs do 120 to 150 IOPS. SSDs 10,000 to 30,000 IOPS." Because of this overwhelming speed advantage many large corporate customers are opting for SSDs, despite the significant price premium SSDs command compared with HDDs.

Regarding cost, Yang expects to see a 35 percent to 45 percent year-to-year drop in SSD prices. This will be a welcome relief since 64GB SSDs currently can add as much as $900 to the price of a notebook PC.

In the third quarter, Samsung is slated to bring out a 128GB SSD based on MLC (multi-level cell) technology--which uses multiple levels per cell to allow more bits to be stored. But the company sees even larger-capacity SSDs, ranging all the way up to 250GB, possibly before the end of the year.

The company is also working with notebook PC makers to design ultrathin notebooks with SSDs that can fit into potentially even thinner designs than the 0.76-inch thick MacBook Air, which uses SSD.

[ice82]

It's good to hear that the SSD capacity will go up to 250GB soon.
I'll hold onto my laptop until next year for that 100GB+ SSD.

[Seaspray0]

So what is the typical write pattern for one of these drives being used instead of a standard platter hard drive? Many of the files get stored for long term without change and those areas would only receive limited writes compared to unallocated space. As the drive space is consumed to near capacity this would become a more critical issue. What then? Under those conditions, what would the expected lifetime of the flash hard drive be? Would a combination of the two be better? i.e. One platter drive for the OS (where read/write catching of virtual memory is highly active) and one flash drive for data storage.

[zag2]

I've had a Samsung 32gb SSD in my home theater computer for 6 months now, absolutely no trouble with reliability and the speed increase is massi ve. It boots in 20 seconds and launching applications is instant. Its actually very frustrating going back to a computer with a normal hard disk and waiting 1-2 seconds for apps like firefox and IE to load.

These things will revolutionize the server market if they are indeed more reliable than standard hard disks.

[nvmexpert]

What made you buy a SSD for a home theatre computer? It's funny that you think 1-2 seconds is frustrating :-)

[nvmexpert]

"He added that if a failure ever does occur, it will not occur in the flash chip itself but in the controller"

Are you saying that Samsung SSD's have a controller issue? How long does it take for them to fail???

[zag2]

I would expect its exactly the same probability of a HDD controller failing, Just without the risk of the mechanical parts wearing out.

[kokenge]

In Oct, 2007 i purchased 10 Dell D830 laptop for my company with the 64GB ssd. Two issues:
1) while their ramdom access speeds are indeed awesome, their sustained read/writes are pathetic. They will boot quickly, but try to open a simple 30 MB ppt, and you are waiting a while.

2) after 1.5 years, I am replacing all of them. Their speeds seem to have deteriorated over time. Worn out perhpas?

I am in the process of striping 5 ssd together in a server to test that setup. It should solve the speed issues while gaining the benefit of quick ramdom access.