Avoid SSDs with Jmicron’s JMF602 Controller

Solid state drives (SSDs) are the latest in hot tech upgrades these days, and rightly so. SSDs add huge boosts in performance to a system that is HDD bound, and the storage subsystem of a computer is the weakest link in its performance.

It's no wonder that SSDs are becoming increasingly popular. However, not all SSD drives are made alike. Don't think that you'll get great performance just by swapping out your old HDD for a new SSD. The first thing to consider is whether or not you'll want a MLC (multi-layer cell) or SLC (single-layer cell) drive. MLC SSD drives store more data, but at the cost of read and write performance, with a big dip on write performance. SLC drives rule in speed, but currently come in smaller capacities.

No matter which type of SSD you decide to pick up, you will no doubt witness instant performance gains after installing your new drive. However, with SSDs, things aren't so simple. Because of the way SSDs work, you will witness a steep degradation in performance over time. The performance occurs from a combination of things, but not because of file defragmentation like on a regular disc-based HDD.

With a regular HDD, you can simply run a good defragmentation utility to optimize the drive back to optimized conditions, and immediately experience the performance gains. On an SSD, you should never defrag the drive due to wear and tear of the flash memory cells. But this is only part of the problem. Another big problem with many SSD drives on the market is their use of the Jmicron JMF602 drive controller.

We'll just go ahead and say it right here: the controller is terrible.

First, the Jmicron JMF602 controller only has a 16 KB of onboard cache. That's barely enough to do anything. Contrary to this, the controller that Intel uses, the PC29AS21A blows the Jmicron controller out of the water with 256 KB of cache. The Intel controller also has significantly better wear leveling and write combining algorithms.

During heavy use, the Jmicron controller will literally choke on incoming data, and consequently report back to the operating system that it's buffers are filled and writes and reads need to be queued up. This puts a hold on incoming and outgoing disk I/O, causing applications to hiccup and hang while the controller chugs along. Worst, the performance degrades significantly over time as the drive is used.

Recently, OCZ swapped out the Jmicron controllers in its drives in favor of Indilink's Barefoot controller, offering significantly better performance and cell management algorithms. Other manufacturers are following suit as well.

If you're in the market for an SSD, do a bit of research to find out if the drive uses a Jmicron controller. News from Jmicron is that its updated to a new revision of its SSD controller that is suppose to solve many issues. Save yourself the problem of testing out these claims and just avoid Jmicron-based drives altogether.

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  • Fox Montage
    This is useful information, good job. But ahem, "Save yourself the problem of testing out these claims and just avoid Jmicron-based drives altogether." Isn't this your job? lol Let's give them a chance!
  • wild9
    Looks like the issues with SSD's aren't confined to Jmicron controllers, namely the technology itself is rather flawed at this stage. Who wants to invest in a storage device that degrades over time, and risks data loss?

    I really want this technology to mushroom, and I think it will. It's just that at this stage in the game it's like producing a new form of fuel, knowing that fuel is going to wreck your car after a few months..maybe if the manufacturers got together and bashed out some design protocols (that are 99% stable and efficient), it wouldn't be left to the consumers to do the beta testing.