Thoughts on the future of technology in and out of the datacenter

Pure Mystery Series – PART 2: eMLC vs Consumer MLC

Pure Storage Mysteries……Demystified……

Question 2:  “I heard Pure Storage uses 100% consumer cMLC flash devices?  Is that true?”
You are correct, our data devices are comprised of 100% consumer based flash devices (cMLC), not enterprise flash devices (eMLC).  Our cMLCs paired with highly intelligent software (built from the ground up on flash) gets us closer and closer to the cost of disk.  Mix in some dedupe, compression, and pattern removal and Pure Storage has solved the cost puzzle of flash.  100% flash for the cost of disk……no brainer…

What is the difference between eMLC and cMLC?
eMLC and cMLC are actually comprised of the same flash chips.  The only real difference between them are the amount of over provisioned capacity (typically 28%-60% for eMLC vs 8%-10% in cMLC) and CPU size.  eMLC was born when storage controllers only understood disk.  Disk vendors could not completely revamp their IO complex to work with flash, so their only option was SLC flash (with a huge cost and tons of program/erasure cycles).  To get the price down from SLC, SSD vendors determined that if they put intelligence and larger CPUs in MLC devices they could then handle enterprise class workloads without any update to the storage IO complex or added intelligence.  Making dumb controller smart via smart SSDs.  It worked out well for the SSD vendors, as they were able to charge a significant premium for cMLC, just because it contained the intelligence that the storage controller probably should have already had, before implementing flash.

Where are eMLC and cMLC devices deployed?
eMLC devices are typically deployed in a storage system originally built on a disk or a system without the intelligence to write to these devices in a way that extends their longevity.  On the other hand, cMLC devices are typically found in storage systems that are highly intelligent, efficient, and built from the ground up on flash.

Below is a quick comparison to your traditional eMLC flash array versus Pure Storage.  Remember, over provisioned capacity is capacity you pay for, but cannot use.

Pure Storage:

  • cMLC over provisioning (garbage collection / wear leveling):  8%-10%
  • Systems over provisioning (system activities / hot sparing):  20%

eMLC Competitor:

  • eMLC over provisioning (garbage collection / wear leveling):  28%-60%
  • Systems over provisioning (system activities / hot sparing):  20%

Difference = Pure 28% vs eMLC Competitor 48% = 20% More Efficiency  (Pure Storage Advantage….again)

How do you get to 28% over-provisioning for eMLC?  
eMLC devices today typically come in 200GB or 400GB, yet they are actually 256GB or 512GB devices.  So the calculation is:  (256 – 200) / 200 = 28% OR (512 – 400) / 512 = 28%…  cMLC is 8 – 10% over provisioned in all devices.  Comically enough, we see eMLC devices that are actually 60% over provisioned……what a waste!

But I thought SLC and eMLC were the only “Enterprise Class” flash devices?
Not true at all.  Trust me, if our competitors could get cMLC to work, they would use it too.  The fact that we make cMLC work and stay more reliable than anyone in the market (we have non-disruptive everything) gives us a HUGE competitive advantage against our competitors.  What typically fails in flash devices is the firmware.  The awesome part about cMLC is that it is found in millions of consumer based devices, and in turn manufacturers rigorously test cMLC drives to avoid early failures and widespread issues in millions of devices.  Since the high end SLC and eMLC drives are sold 100x less often, they are tested less in the field and in turn contain a much higher frequency of bugs in their firmware.  Also, our testing of both SLC, eMLC, and cMLC flash we found the failure rates to be 10x worse on eMLC versus cMLC due to firmware issues.

So how does Pure Storage make cMLC work?
At Pure Storage we created a platform (Purity) from the ground up with all the features needed to support cMLC flash.  Purity efficiency writes only unique and compressed data to cMLC flash, wear levels the devices, and manages IO effectively.  With all of this at play it dramatically increases it’s life and performance to the same, if not better, than an eMLC device.  Since Purity provides a robust set of features the value of eMLC devices is diminished and would only increases the cost of our solution.  Our FlashCare provides the following:

Seems pretty awesome……so what’s next?
At the end of the day, IT IS ALL ABOUT THE SOFTWARE.  And the cMLC is not an end point for Pure, it is just the beginning.  You can bet our engineering team is hard at work implementing the next super dense, super inexpensive flash modules for future capabilities.  It only gets better from here.  Our intelligent software understands how flash works and utilizes all of its capabilities and provides intelligence for all of its weaknesses.  The question is, does that eMLC solution you are looking at have the software intelligence you expect for your next generation storage solution?  Is that a long term solution?  Or will you be stuck buying super expensive eMLC devices forever, because they don’t have enough software intelligence to support cMLC devices?  With Pure Storage you will never have that concern.  

One thing is for certain….those spinning things…..are dead  🙂

Until next time…..  Stay flashy my friend…….