The Return of the JMicron based SSD

With the SSD slowdown addressed it’s time to start talking about new products. And I’ll start by addressing the infamous JMicron JMF602 based SSDs.

For starters, a second revision of the JMF602 controller came out last year - the JMF602B. This controller had twice the cache of the original JMF602A and thus didn’t pause/stutter as often.

The JMicron JMF602B is the controller found in G.Skill’s line of SSDs as well as OCZ’s Core V2, the OCZ Solid and the entire table below of SSDs:

JMicron JMF602B Based SSDs
G.Skill FM-25S2
G.Skill Titan
OCZ Apex
OCZ Core V2
OCZ Solid
Patriot Warp
SuperTalent MasterDrive

 

All I need to do is point to our trusty iometer test to tell you that the issues that plagued the original JMicron drives I complained about apply here as well:

Iometer 4KB Random Writes, IOqueue=3, 8GB sector space IOs per second MB/s Average Latency Maximum Latency
JMF602B MLC Drive 5.61 0.02 MB/s 532.2 ms 2042 ms

 

On average it takes nearly half a second to complete a random 4KB write request to one of these drives. No thanks.

The single-chip JMF602B based drives are now being sold as value solutions. While you can make the argument that the pausing and stuttering is acceptable for a very light workload in a single-tasking environment, simply try doing anything while installing an application or have anti-virus software running in the background and you won’t be pleased by these drives. Save your money, get a better drive.

The next step up from the JMF602B based drives are drives based on two JMF602B controllers. Confused? Allow me to explain. The problem is that JMicron’s next SSD controller design won’t be ready anytime in the near future, and shipping mediocre product is a better option than shipping no product, so some vendors chose to take two JMF602B controllers and put them in RAID, using another JMicron controller.


Two JMF602B controllers and a JMicron RAID controller

The problem, my dear friends, is that the worst case scenario latency penalty - at best, gets cut in half using this approach. You’ll remember that the JMF602 based drives could, under normal load, have a write-latency of nearly 0.5 - 2 seconds. Put two controllers together and you’ll get a worst-case scenario write latency of about one second under load or half a second with only a single app running. To test the theory I ran the now infamous 4K random write iometer script on these “new” drives:

Iometer 4KB Random Writes, IOqueue=3, 8GB sector space IOs per second MB/s Average Latency Maximum Latency
JMF602B MLC Drive 5.61 0.02 MB/s 532.2 ms 2042 ms
Dual JMF602B MLC Controller Drive 8.18 0.03 MB/s 366.1 ms 1168.2 ms

 

To some irate SSD vendors, these may just be numbers, but let’s put a little bit of thought into what we’re seeing here shall we? These iometer results are saying that occasionally when you go to write a 4KB file (for example, loading a website, sending an IM and having the conversation logged or even just saving changes to a word doc) the drive will take over a second to respond.

I don’t care what sort of drive you’re using, 2.5”, 3.5”, 5400RPM or 7200RPM, if you hit a 1 second pause you notice it and such performance degradation is not acceptable. Now these tests are more multitasking oriented, but if you run a single IO on the drive you'll find that the maximum latency is still half a second.

The average column tells an even more bothersome story. Not only is the worst case scenario a 1168 ms write, on average you’re looking at over a quarter of a second just to write 4KB.

The G.Skill Titan has recently garnered positive reviews for being a fast, affordable, SSD. Many argued that it was even on the level of the Intel X25-M. I’m sorry to say it folks, that’s just plain wrong.


One of the most popular dual JMF602B drives

If you focus exclusively on peak transfer rates then these drives work just fine. You’ll find that, unless you’re running a Blu-ray rip server, you don’t spend most of your time copying multi-GB files to and from the drive. Instead, on a normal desktop, the majority of your disk accesses will be small file reads and writes and these drives can’t cut it there.

Some vendors have put out optimization guides designed to minimize stuttering with these JMF602B based drives. The guides generally do whatever they can to limit the number and frequency of small file writes to your drive (e.g. disabling search indexing, storing your temporary internet files on a RAM drive). While it’s true that doing such things will reduce stuttering on these drives, the optimizations don’t solve the problem - they merely shift the cause of it. The moment an application other than Vista or your web browser goes to write to your SSD you’ll have to pay the small file write penalty once more. Don’t settle.

But what option is there? Is Intel’s X25-M the only drive on the market worth recommending? What if you can’t afford spending $390 for 80GB. Is there no cheaper option?

Latency vs. Bandwidth: What to Look for in a SSD OCZ Tries Again with the Vertex
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    What about e.g. CRC? How does possibility of data corruption compare to traditional SSD? What about RAID? Since the drives are electrical, not mechanical, this reduces the number of failure vectors and environmental concerns Reply
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