Measuring Write Endurance: SLC Wins Again
Most customers will never even come close to exceeding the write endurance limits of today's desktop-oriented SSDs. Write exhaustion requires continuous writing to a drive for weeks and months on end before you completely consume the usable life of each NAND cell. In the enterprise world, however, this is a much more likely scenario. Knowing the write endurance of an SSD can help IT professionals select drives that are best suited to their tasks.
This is a metric we're expecting to set Micron apart from its competition. The company chooses to use 34 nm SLC flash in its P320h, and that decision is impactful in two ways.
The first is write endurance. Typically, SLC is capable of 100,000 program/erase cycles, while eMLC is closer to 30,000. The MLC memory most commonly used today falls between 3,000 and 5,000 P/E cycles. In our testing, SLC (even from different manufacturers) consistently performs better than its rating. Micron's NAND is no exception. It doesn't come cheap, though. The RealSSD P320h runs roughly $10/GB.
Before we dig into the results, if you are unfamiliar with the different types of NAND or the concept of write exhaustion in general, take a look at Intel SSD 910 Review: PCI Express-Based Enterprise Storage.
In order to test write endurance, we write large-block, sequential data to the drive and continuously monitor the Percentage Lifetime Used SMART attribute. This tells us, on a scale from 0 to 100, the percentage of life exhausted from the drive's NAND. We started with a clean drive and wrote to it until the attribute reached 1%.
By writing sequential data, we demonstrate the maximum usable life of the flash, removing variables like wear-leveling and garbage collection. In this configuration, write amplification should be very close to 1.0x. We did run into an issue, though, that complicated testing. Mainly, Micron does not provide a SMART attribute that reports the total amount of data written to the drive. This definitely caused some concern because we had no way of knowing how much data had been written previously, which could have skewed our results. Normally, we rely on our testing software to keep track of this, but we always like to double-check our work. This could be a concern for system administrators that want a hard number. For most, though, the SMART attributes provided should be sufficient to successfully administer the P320h.
|Endurance RatingSequential Workload, QD=1, 8 MB, Random
|Row 0 - Cell 0
|Micron Real SSD P320h
|Intel SSD 910
|Micron 32 nm SLC
|Intel 25 nm eMLC (HET)
|Intel 50 nm SLC
|Toshiba 32 nm SLC
|RAW NAND Capacity
|IDEMA Capacity (User Accessible)
|22% (12.5% RAIN)
|P/E Cycles Observed (IDEMA)
|P/E Cycles Observed (Raw)
|Host Writes per 1% of MWI
If you only consider write endurance and cost in dollars per petabyte written ($38), ignoring all else, the RealSSD P320h is our new champion. Based on our results, the P320h is clearly the best choice for customers who need a write-caching solution with high endurance for a reasonable price.
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my wallet just had a heart attack, this thing would be freaking amazing to haveReply
i dont see this as the future of consumer SSD's, just like a 16 core CPU is not the future of consumer CPU's.Reply
mayankleoboy1i dont see this as the future of consumer SSD's, just like a 16 core CPU is not the future of consumer CPU's.Reply
Such an apples to oranges comparison...
Eliminating the SAS controller is the logical way to have these pci-e based ssd drives...Reply
Kinda surprised something like this didn't come out first as it makes more sense....
bawchicawawaSuch an apples to oranges comparison...Reply
really ? Increasingly, performance is basically dependent on extracting parallelism. Whether in storage or in CPU performance.
Desktop/Mainstream users just dont do so much in parallel that they can fully use all the hardware.
mayankleoboy1i dont see this as the future of consumer SSD's, just like a 16 core CPU is not the future of consumer CPU's.I see a purpose for 16 core processors. How are we going to otherwise be able to run Crysis 6?Reply
JOSHSKORNI see a purpose for 16 core processors. How are we going to otherwise be able to run Crysis 6?Reply
Use a 5000 core GPU ?
ArticleAlthough read performance is out of this world, the RealSSD P320h's write performance isn't nearly as spectacular. That's not to say the drive doesn't do well; it's just not as impressive after looking at those massive read numbers. read performance was out of this world, the write performance wasn't nearly as spectacular. Now, that's not to say that the P320h doesn't perform well, it's just not as impressive as the read resultsReply
After all these years it's nice to see the OCZ Revo at least mentioned. Considering a bootable PCI-E x4 SSD can be had for under $200 for over 5 years now, and is on it's 4th+ generation, one can only wonder why it's been ignored for so long.Reply
Micron deserves a pat on the back for this one!Reply
Thanks for the review, love to see this kind of advancement and a peak into the future new hardware brings with it, even if it isn't directly applicable to me at this point in time.