Comment by hackuser | Hacker News Reader

Comment by hackuser | Hacker News Reader

There's something I don't understand about the enterprise vs consumer (or "client") SSD classification: According to the widely quoted JEDEC standard, JESD218A, [0] these are the date retention standards:

Retention Use (power off):

* Client: 30° C, 1 year

* Enterprise: 40° C, 3 months

It's not a typo, I've seen it in many places: It appears that the power-off data retention standard is only 3 months in enterprise drives (1 year in client drives isn't great either).

Can anyone explain it? My only guess is that the "enterprise" classification refers to drives designed to churn data 24/7, not store it long-term. But I think many people understand the term 'enterprise' to mean much greater durability. I'd be very disappointed if I experienced dataloss from leaving any drive on a shelf for 3 months, much less an expensive enterprise drive. (Or maybe I misunderstand what's meant by Retention Use (power off)?)

[0] Available here: https://www.jedec.org/standards-documents/results/jesd218b.0... and quoted here in the table here: http://www.kingston.com/us/ssd/enterprise/best_practices/ent...

Retention is related to temperature. Consumer drives may last less than 3 months at 40 C, and enterprise drives may last more than 1 year at 30 C. Both may last even longer at 20 C.

How many studies have been done verifying that enterprise SSDs perform significantly better than consumer SSDs in any metrics?

My belief is that the consumer SSDs actually have very similar performance and reliability requirements to the enterprise because they are generally deployed without redundancy, and so any failures can be catastrophic for consumers. And then there are lots of consumers that will go on Amazon or Newegg etc. and leave very bad reviews.

So I personally believe the 'enterprise' distinction is mostly a scam, and developers who are looking for inexpensive hosting have been mainly waiting for A) datacenter providers to realize that or B) a slow market perfusion that mitigates it.

> How many studies have been done verifying that enterprise SSDs perform significantly better than consumer SSDs in any metrics?

Define perform. But short answer, lots.

To be fair, consumer SSDs these days are pretty solid, and will perform great for most workloads - even many workloads which enterprise drives would be used for.

The big difference though, is with extremely heavy write workloads. The endurance of enterprise SSDs in terms of how much data you can write before the drive will fail, is a couple orders of magnitude greater than consumer drives. For example, I have an 800gb Intel S3710 SSD. It's rated to handle 10 DWPD (drive writes per day) - meaning that one could write 8,000 gigabytes of data a day, 365 days a year, for 5 years (~17 petabytes), and the drive will still be chugging away just fine.

A 1TB Samsung 850 Pro (which has some of best endurance of consumer ssds), on the other hand is only rated to 300 terabytes of data written. So the enterprise drive has a 60x improvement in endurance.

Do those ratings reflect actual tested durability or mainly marketing?

What is the real average durability requirement?

Have there not been some relatively large providers using consumer SSDs in the datacenter successfully for some time?

> Do those ratings reflect actual tested durability or mainly marketing?

They reflect what the manufacturers will offer the warranty until. A quick google search suggests about 2 petabytes of writes is the max you can get on a samsung 850 before it completely fails (and after 1 petabyte you will have many failed sectors and data corruption starts creeping in)

At the same time, I bought my S3710 used and when I got it, it had almost 8 petabytes written and it's still just like new.

> Have there not been some relatively large providers using consumer SSDs in the datacenter successfully for some time?

Yes, that wouldn't surprise me at all. Like I said, for many workloads, consumer SSDs are acceptable. But that doesn't mean enterprise drives are a scam.

I noticed that the Samsung 960s are rated at almost exactly 0.3 DWPD, which happens to be the standard endurance for "read-optimized" SSDs, even across different generations of flash. This looks more like market segmentation than a measurement.

It's rated to handle 10 DWPD (drive writes per day) - meaning that one could write 8,000 gigabytes of data a day, 365 days a year, for 5 years (~17 petabytes), and the drive will still be chugging away just fine.

It actually means something more like "we don't feel confident that the drive will last more than 5 years at 8TB/day." --- and if you do the maths, assuming perfectly even wear, this means they're rating the flash at ~20K cycles/cell, which sounds a bit ambitious for 20nm MLC considering that ~10K cycles was the norm for 65nm MLC several years ago.

1TB Samsung 850 Pro (which has some of best endurance of consumer ssds), on the other hand is only rated to 300 terabytes of data written.

That totals around 300 cycles/cell, which seems like 3-bit/cell ("TLC") flash to me, or cheap small-process MLC.

One big difference (from my experience) is that consumer SSDs would go into the market first while enterprise products would continue to test for 6-12 months for more maturity. The consumer SSDs would go through frequent updates of firmware and flash revisions while the enterprise products would be frozen for much longer. With an agreement, you can guarantee the exact same product is available many years later. When I used to do SSD firmware development, I would back-port particular fixes to an older version of firmware so a customer could minimize risks of changes. For consumer side, we would just say try out the latest version.

I think the market is going through a shift as more redundancy is used at the server level and the SSDs are considered more as a commodity.

As Kephael and the article point out, one clear advantage of enterprise drives is that they typically have capacitors that allow them to clear their caches in the event of power loss.

> How many studies have been done verifying ...

With due respect, what verifies the allegations in the comment?

While the enterprise vs consumer distictions seems to have been mostly a labeling and market segmentation exercise of the past (now we have a more differentiated landscape with NAS 24/7 etc), the story for SSDs is different.

From the technology side, there is at least the amount of extra flash that the drive contains and that it can use for better performance and longer life times (TBW rating).

Our anecdotal experience is that there is quite a noticable difference between drives: - 99.5 percentile latency during normal operations. Some enterprise drives guarantee response times, others are all over the place. Note that consumer drives often claim a much higher maximum IOPS rating whereas you can get enterprise drives with a sustained rating. - drives hanging for >60s, presumably during internal cleanup. - firmware stability, drive getting unresponsive when maxing it out over longer periods.

Those are the same retention ability for typical flash. Every 5C of storage temperature cuts data life in half. (A higher write temperature can lessen this, but you wouldn't want to depend on it in a typical server scenario.)

But they don't want to assume all devices will behave that way. Better to specify the server scenario at realistic server temperatures.

I think "enterprise" really means "designed for living in a datacenter", with its accompanying temperature-controlled environment. If you want durability/reliability/ruggedness, "industrial" is the keyword to look for.

For hard drives, 'enterprise' has traditionally referred to durability. For example, they've had a much higher MTBF.

It's been mentioned below that differences in temperature matter a lot. But there's also the fact that erasing a flash block inherently damages it, progressively reducing its ability to retain data.

So I wonder if there's a tradeoff between longer data retention when powered off (by using higher write and erase voltages) and longer MTBF (by using lower voltages). I could be completely wrong here, but if there is such a tradeoff it would make sense for consumer and enterprise drives to make different choices.

On that note I've always wondered if putting an SSD in an oven at the highest temperature just before damaging it could revive it from being written to and erased too many times.

The same mechanism that makes SSD's not retain data (that is, the electrons escaping) and the same thing which makes them not retain the data that you do want to keep would presumably also make the electron buildup that you get that kills the cells abilities to continue their write/erase cycle.

A consumer drive will spend its live either powered on or at "room temperature", but an enterprise drive is very likely in a data center inside a server or disk array, and much more likely to experience higher temperatures even when powered down.

Reading this i really wish that Sony was not so bloody proprietary with their multi-disc BD storage format.

The main difference is enterprise drives support time limited error recovery, this is a feature that allows for reliable use in conjunction with a hardware RAID controller.

It seems I misread the question, TLER is what typically differentiates an enterprise hard disk from a consumer hard disk. The primary differentiator between an enterprise SSD and consumer SSD has typically been write endurance.

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