Endurance is a term thrown around a lot in discussions of solid-state storage because we all worry about that point where an SSD is no longer able to reliably store our data. If you have an SSD in your notebook or mainstream desktop, endurance shouldn't be much of a concern. It's unlikely that you'll ever write enough data per day, every day, to exhaust the useable life of the NAND flash cells that make up your drive. Far more likely is a firmware-related issue that results in problematic operation. But even those are fairly rare.
Endurance is a much more important discussion in the enterprise world, though. Demanding workloads force many machines to read or write data continuously, day in and day out. On a conventional hard drive, other issues contribute to eventual failures. But when it comes to SSDs, those business-oriented tasks gradually chip away at the rated number of program/erase cycles that each NAND vendor affixes to its memory products. Because eMLC and SLC flash offer the highest endurance ratings, they're particularly attractive for enterprise-oriented products.
That's not to say multi-level cell NAND is out of place in professional applications. Based on our discussions with data center managers, we know there are plenty of original X25-M and SSD 320s used in mission-critical environments. They are used in such a way that a failure won't result in data loss, though, and they aren't bombarded with writes in the same way one of these Toshiba drives might be.
Evaluating SSD Endurance
Before we take a stab at quantifying the endurance of different flash technologies, we want to discuss our methodology. Our estimates come from monitoring each drive's media wear indicator (referred to as the MWI), which counts down from 100 to 1. Because the number of program-erase cycles a NAND cell can withstand is finite, the MWI is designed to facilitate a rough estimate of endurance.
In theory, once you reach the end of the counter, all of the memory's rated P/E cycles are exhausted. That's not to say something bad happens when you hit the bottom, but nobody wants to entrust irreplaceable data to a drive living on borrowed time, either. Naturally, enterprise customers place a lot of importance into the MWI, then, because it represents “the safe zone.”
| Endurance Rating (Sequential Workload, QD=1, 2 MB) | Intel SSD 320 | Intel SSD 710 | Toshiba MK4001GRZB |
|---|---|---|---|
| NAND Type | Intel 25 nm MLC | Intel 25 nm eMLC (HET) | Toshiba 32 nm SLC |
| RAW NAND Capacity | 320 GB | 320 GB | 512 GB |
| IDEMA Capacity (User Accessible) | 300 GB | 200 GB | 400 GB |
| Overprovisioning | 7% | 60% | 28% |
| P/E Cycles Observed (IDEMA) | 5460 | 36 600 | 225 064 |
| P/E Cycles Observed (Raw) | 5119 | 22 875 | 175 831 |
| Host Writes per 1% of MWI | 16.38 TB | 73.20 TB | 900.2 TB |
According to Toshiba's spec sheet, the 100 GB MK100GRZB comes with an endurance rating of 8.2 PB. Each vendor uses its own method of estimating longevity, which is why it’s difficult to compare endurance across different SSD brands and models. Our numbers assume a purely sequential workload, which means we’re ignoring random access. However, this allows us to take a step back and look at SSD and NAND endurance academically.
Look at the numbers. It’s really clear to see why SLC flash remains the crème of the crop. While it continues to fetch a high premium, SLC is also capable of withstanding many more writes than MLC technology. If you remove the effects of overprovisioning, the Toshiba’s SLC NAND has a rating close to 175 000 P/E cycles. That’s 58 times higher than Intel’s 25 nm MLC NAND, which clocks in at ~5000 P/E cycles.
Remember that P/E-cycle ratings apply to each flash cell. But because larger SSDs employ more NAND (and consequently, a lot more flash cells), it takes longer to write across all of them. As a result, larger drives enjoy a higher endurance rating. If we do the math, our 400 GB MK4001GRZB should be capable of writing 88 PB of data sequentially. That’s insanely high. And perhaps it explains why Toshiba doesn’t provide endurance ratings on its higher-capacity SSDs. Instead, the 200 GB and 400 GB models come with a guarantee that you won’t have to worry about endurance during the company's five-year warranty period (a telling promise, indeed).
- Toshiba's SAS-Based Enterprise-Class SSD
- Endurance: Comparing MLC, eMLC, And SLC
- Test Setup And Benchmarks
- Benchmarking For The Enterprise: A Whole New World
- 4 KB Random Performance
- 128 KB And 2 MB Sequential Performance
- Power Consumption
- Enterprise Workload Performance
- MK4001GRZB : Great Endurance, Fast Reads, Slower Writes

...fullish of cash? Definitely. Foolish? Probably not.
You've clearly not understood the purpose of this article. Stick to commenting the desktop drive reviews in the future, please.
Thank you for this review, and especially your estimations on the endurance of the drive. It's something that's damn near impossible for us IT professionals to get accurate estimations of in the real world. For some reason, bosses tend to want the expensive hardware to be put to use instead of being thoroughly tested.
More of these types of articles please! :]
Perhaps the Enterprise SSD Fairy will bring you a Hitatchi UltraStar with Intel's 6gbps controller. I'd be eager to see how it compares.
There is no substitute for SLC though.
...fullish of cash? Definitely. Foolish? Probably not.
damn the english language.....there are way to many words that sound alike
You've clearly not understood the purpose of this article. Stick to commenting the desktop drive reviews in the future, please.
Thank you for this review, and especially your estimations on the endurance of the drive. It's something that's damn near impossible for us IT professionals to get accurate estimations of in the real world. For some reason, bosses tend to want the expensive hardware to be put to use instead of being thoroughly tested.
More of these types of articles please! :]
Even when the INTEL SSD already has an endurance longer than your refresh cycle for your tech stack?
"Back in my days storage drives used to have moving parts. Now its all solid state."
Unlike super-sized enterprise which I am not, the cost/benefit calculations would be difficult for myself. I know firsthand the money that i.e. financial institutions push into their data centers, and for those folks $7K isn't out of the question.
Interesting SSD and if the prices come down and warranty extended then IMO it would be something to consider and compare against Intel's products.
I was not disappointed.
I refer you to the ~$20,000 1.2TB fusion-io SSD's.
but wow... $7000...
I go with 10 of 128GB SSD....
Hell I'll gladly pay that much because drives like this save money in the long run. They are cheaper and much easier to set up and maintain vs hundred of mechanical drives in a raid setup. In power alone over the live of the drive vs mechanical drives adds up. So $7k isn't that bad and this isn't the most expensive SSD that I have seen.
Throw 50TB daily writes on that Intel SDD array of yours and it will last you only 3 months until full failure.
"Hey uh, our entire rack of $50 SSDs simply died on us, along with all of our business files."
Throw 3 Intel MLC 480 GB SSD's in RAID-5 (1k each), make an agressive overprovisioning...and they will both last MUCH longer and also run circles to this expensive piece of hardware being reviewed.
Heck, it's pretty much touching Fusion-IO pricing without even coming close on speed.
This will only work for people needing plug & play replacement for their SAS drives AND with very deep pockets. Since i suspect the replacement should be made in batches...it will be VERY expensive.
Anyone else with brains can find a lot of cheaper, faster AND more reliable solutions.
I'd wait for a Velodrive, raid a couple of them and just have regular backups on a storage with regular HDD's (that is, read GB/s from a couple SSD's...write GB/s sequentially to a storage).
I do understand though that there are out there companies that can't risk innovation and smart choices and have to recur to handwritten promises and warranties of the big guys.
Reason why buying a Dell costs a hell lot more than building it yourself.
Reason why building your own storage is a fraction of the price of an EMC solution.
And so on...
For $7000 that is the first thing I would have done Andrew.
"Why are they called drives, granpa?"