SSD performance -- is a slowdown inevitable?
- — 11 May, 2009 08:50
The recent revelation that Intel Corp.'s consumer-class solid-state disk (SSD) drives suffer from fragmentation that can cause a significant performance degradation raises the question: Do all SSDs slow down with use over time?
The answer is yes, and every drive manufacturer knows it.
Here's the rub: Drive performance and longevity are inherently connected, meaning drive manufacturers work to come up with the best balance between blazing speed and endurance. And since SSDs are fairly new to the market, users are finding that while they do offer better speed in some ways than hard disk drives, questions remain about how much of that speed they deliver for the long haul.
One thing you can be sure of is that the shiny new SSD you just bought isn't likely to continue performing at the same level it did when you first pulled it out of the box. That's important to know, given the speed with which SSDs have proliferated in the marketplace amid claims that they're faster, use less power and can be more reliable -- especially in laptops -- since there are no moving parts.
They also remain more expensive than their spinning-disk hard drive counterparts.
"An empty [SSD] drive will perform better than one written to. We all know that," said Alvin Cox, co-chairman of the Joint Electron Device Engineering Council's (JEDEC) JC-64.8 subcommittee for SSDs, which expects to publish standards this year for measuring drive endurance. Cox, a senior staff engineer at Seagate, said a quality SSD should last between five and 10 years.
The good news is that after an initial dip in performance, SSDs tend to level off, according to Eden Kim, chairman of the Solid State Storage Initiative's Consumer SSD Market Development Task Force. Even if they do drop in performance over time -- undercutting a manufacturer's claims — consumer flash drives are still vastly faster than traditional hard drives, because they can perform two to five times the input/output operations (I/Os) per second of a hard drive, he said.
Coming soon, standards and specs
In May 2008, the JEDEC subcommittee co-chaired by Seagate and Micron, held its first meeting to address the standards development needs of the still-emerging SSD market.
JEDEC is among several groups working to publish either standards or specifications for the drives by year's end. Along with IDEMA (International Disk Drive Equipment and Materials Association) and the SSD Alliance, headquartered in Taipei, Taiwan, the Storage Networking Industry Association's (SNIA) Solid State Storage Initiative plans to publish performance specifications no later than the third quarter for vendors to adopt and eventually use on their SSD packaging.
SNIA's specifications will set up standard benchmarks for measuring new drive performance and degradation over time, depending on the applications being used.
Phil Mills, chairman of the Solid State Storage Initiative, said the performance numbers most manufacturers use now for marketing represent a drive's "burst rate" — not its steady state or average read rate. "So there's already a huge difference between out-of-the-box versus constant use," he said. "And then, in both burst mode and steady state, there are huge differences in performance between manufacturers."
Because SSDs have no moving parts, when the drives go bad -- and they do on occasion — what users are apt to see are failures at the controller or chip level where firmware bugs can affect I/O operations with a computer's operating system. With such relatively new technology, hiccups are possible.
For example, a Computerworld editor who purchased a 120GB SSD from OCZ Technology last month, found that the drive failed after only two weeks of use. He's now using a replacement -- and backing up data often.