SSD reliability in the real world: Google's experience

Using data from millions of drive days in Google datacenters, a new paper offers production lifecycle data on SSD reliability. Surprise! SSDs fail differently than disks - and in a dangerous way. Here's what you need to know.

SSDs are a new phenomenon in the datacenter. We have theories about how they should perform, but until now, little data. That's just changed.

The FAST 2016 paper Flash Reliability in Production: The Expected and the Unexpected, (the paper is not available online until Friday) by Professor Bianca Schroeder of the University of Toronto, and Raghav Lagisetty and Arif Merchant of Google, covers:

  • Millions of drive days over 6 years
  • 10 different drive models
  • 3 different flash types: MLC, eMLC and SLC
  • Enterprise and consumer drives

Key conclusions

  • Ignore Uncorrectable Bit Error Rate (UBER) specs. A meaningless number.
  • Good news: Raw Bit Error Rate (RBER) increases slower than expected from wearout and is not correlated with UBER or other failures.
  • High-end SLC drives are no more reliable that MLC drives.
  • Bad news: SSDs fail at a lower rate than disks, but UBER rate is higher (see below for what this means).
  • SSD age, not usage, affects reliability.
  • Bad blocks in new SSDs are common, and drives with a large number of bad blocks are much more likely to lose hundreds of other blocks, most likely due to die or chip failure.
  • 30-80 percent of SSDs develop at least one bad block and 2-7 percent develop at least one bad chip in the first four years of deployment.


Read more: SSD reliability in the real world: Google's experience | ZDNet
 
What about personal experience, with SSD's from different vendors (manufacturers).

I was very reluctant, to invest money in a totally new technology. I know, I know, Flash Memory has been around for a while, but using it as a replacement for a real hard drive is comparatively new. Storing data on a flash drive is a lot different than how an SSD (replacing as a hard drive) works.

My first SSD, purchased directly from 'PNY' worked for about three months, then one morning refused to boot. It could not even be accessed.
I called PNY customer support, but they refused to give me any assistance at all. It was like "Sorry Charlie!".

I ordered a new SanDisk SSD from Amazon the same day, and it was here in three days. That was over 8 months ago and the SanDisk SSD is working flawlessly, and their SanDisk Dashboard (software) is a valuable tool, running TRIM on a set schedule. After 8 months, the Dashboard reports that my SSD is still 100% usable.

I've spent years working with memory chips, and I definitely know that there are huge differences between chips made by different companies.
I always try to buy memory chips ONLY from known reliable vendors.

Cheers Mates!
TechnoMage :cool:
 

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