New Samsung 840 EVO employs TLC and pseudo-SLC TurboWrite cache

Subject: Storage | July 18, 2013 - 01:12 AM |
Tagged: tlc, ssd, slc, sata, Samsung, cache, 840 evo

Samsung's release of the 840 EVO earlier today likely prompted some questions, such as what type of flash does it employ and how does it achieve such high write speeds. Here is the short answer, with many slides in-between, starting off with the main differences between the 840 and the 840 EVO:

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So, slightly increased specs to help boost drive performance, and an important tidbit in that the new SSD does in fact keep TLC flash. Now a closer look at the increased write specs:

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Ok, the speeds are much quicker, even though the flash is still TLC and even on a smaller process. How does it pull off this trick? Tech that Samsung calls TurboWrite.

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A segment of the TLC flash is accessed by the controller as if it were SLC flash. This section of flash can be accessed (especially written) much faster. Writes are initially dumped to this area and that data is later moved over to the TLC area. This happenes as it would in a normal write-back cache - either during idle states or once the cache becomes full, which is what would happen during a sustained maximum speed write operation that is larger than the cache capacity. Here is the net effect with the cache in use and also when the cache becomes full:

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For most users, even the smallest cache capacity will be sufficient for the vast majority of typical use. Larger caches appear in larger capacities, further improving performance under periods of large write demand. Here's the full spread of cache sizes per capacity point:

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So there you have it, Samsung's new TurboWrite technology in a nutshell. More to follow (along with a performance review coming in the next few days). Stay tuned!

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July 18, 2013 | 01:31 AM - Posted by Tri Wahyudianto (not verified)

Why don't just combine SLC SSD around 16 or 32 gig + HDD with 2 or 3 tera, it will be solution for speed + capacity i think ?

July 19, 2013 | 03:18 PM - Posted by Yuri (not verified)

Closest thing available to what you suggested:

July 18, 2013 | 01:46 AM - Posted by Allyn Malventano

Most likely because to get those speeds they would need multiple channels of it, meaning you can't just slap a single SLC chip in addition to the other flash. This way the parallelism is the same, as a small chunk of each TLC die is used for caching, so the parallelism remains the same. 

July 18, 2013 | 09:38 AM - Posted by Anonymous (not verified)

I would like to know the durability of this drive. especially since these are the first SSDs based on 10nm fab.

July 20, 2013 | 12:17 AM - Posted by Allyn Malventano

For clarity, it's 10nm class flash. In reality it's 19nm. Sure it's in the 10's, but it's not a huge jump from the prior gen stuff. 

July 18, 2013 | 04:10 PM - Posted by Anonymous (not verified)

So Allyn, this ssd has your blessing or not compared to vanilla samsung 840 (non pro)?

I've learned not to buy any SSD without the esteemed Pope Malventano's blessing.

Also, since I have your attention, how do you feel about rolling your own SSHD hybrid similar to what seagate is doing?

Using Intel SRT cache tech, a 64gb SSD, a western digital 2TB black (or higher) and a new Z878 mobo like the Asus Maximus Hero VI?

so I would like to build using a samsung pro ssd for main drive OS and the combo ssd cache drive + WD black for storage.

Your thoughts kind sir? Can you talk about this on the podcast too?

July 20, 2013 | 12:18 AM - Posted by Allyn Malventano

This is Samsung's second gen of TLC, and the first gen stuff wasn't bad. The only question mark is the cache durability and performance, which I will be evaluating as soon as I return stateside. Benchmark results are embargoed for a few more days. 

I'll bring this up in more detail on the podcast, sans Pope hat (sorry).

July 20, 2013 | 10:35 PM - Posted by JWDickieson

How does this stack up against the 840 pro in terms of bang for buck. It's faster at writes compared to the standard 840 but is the 840 pro still there flag ship line.

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