Samsung 840 250GB SSD Review
SLC, MLC, Now TLC
When we look at the SSD market today, there are currently two major barriers to increased adoption – first is cost and second is capacity. Despite recent price cuts bringing SSDs to the lowest prices we’ve ever seen, traditional hard drives such as the Seagate Barracuda 3TB are currently retailing for a mere $0.04/GB, which in comparison to the $0.76/GB found off the Samsung 830 256GB is a lot more capacity for a lot less money.
Now the solution to this problem is fairly complex, but in the most basic way, it almost always involves cramming a lot more stuff into a smaller space. In SSDs for example, moving to a smaller process from say 27nm to 21nm would be a good way to do this. However, with SSDs, it’s also possible to increase the number of bits stored on each cell (transistor), which in turn increases the data that’s capable of being stored. When SSDs were first introduced, we had SLC, or single level cell NAND. This means that only a single bit was stored on each cell, which made capacities fairly low, but durability was fairly high. From that point, we then moved to 2 bit per cell MLC (Multi Level Cell), which saw a significant reduction in terms of cost, a significant improvement in capacity, but a significant reduction in durability as well. This is what brings us to TLC (Triple Level Cell), which is 3 bit per cell MLC. As you may expect then TLC NAND will come with a significant reduction in cost, a significant increase in capacity and of course it should also be expected that it will come with a significant reduction in durability as well. For more in depth information about TLC NAND, be sure check out “Understanding TLC NAND“ by my colleague, Kristian Vättö at AnandTech.
Now, as some of you may know, a couple days ago Samsung held their 2012 Global SSD Summit where they introduced the long awaited successor to their very popular 830 Series SSD, the 840 and 840 Pro Series SSDs. In preparation for the launch, I was able to get a review ready for the enthusiast oriented Samsung 840 Pro 256GB SSD, but unfortunately samples for the general consumer oriented 840 was still unavailable at the time. Since the launch, I’ve received a number of requests on a review for the 840 SSD as Samsung has made it somewhat special. How so you may ask? Well, if you haven’t guessed it yet, they’ve made it the first consumer oriented SSD based off of this “mythical” TLC NAND!
That said, now I’m back stateside and I’ve got the Samsung 840 250GB in for review, so let’s take a look at what this new drive has to offer!
Samsung 840 Specifications
|Samsung 840||Samsung 840||Samsung 840|
|Controller||Samsung S4LN021X01-8030||Samsung S4LN021X01-8030||Samsung S4LN021X01-8030|
|NAND||21nm Toggle Mode 2.0 TLC||21nm Toggle Mode 2.0 TLC||21nm Toggle Mode 2.0 TLC|
|Sequential Reads||530 MB/s||540 MB/s||540 MB/s|
|Sequential Writes||130 MB/s||250 MB/s||330 MB/s|
|DRAM Cache||256MB LPDDR2||512MB LPDDR2||512MB LPDDR2|
|Interface||SATA 3 6GB/s||SATA 3 6GB/s||SATA 3 6GB/s|
|Warranty||3 Years||3 Years||3 Years|
Now before we dive into the review, let’s take a look at the specifications for the new drive. Today, we’ll be reviewing the 250GB edition of the Samsung 840, but it will also come in 120GB and 500GB flavors when it hits store shelves in October. For those wondering why the strange numbers, that’s because the 840 will come out of the box with some level of overprovisioning, which unlike the case with the 830 or 840 Pro, cannot be reduced via the Magician software.
Now my best guess for this is that it’s because the Samsung 840 will use TLC (Triple Level Cell) NAND. Now, Samsung is saying that the durability of TLC NAND should be comparable to MLC (2 bit per cell) NAND, but it seems like Samsung is erring on the side of caution and using some level overprovisioning here to make up for any cells dying or erroring out. One thing to note here is that it’s quite strange that Samsung is giving the various capacities of the 840 different levels of overprovisioning as there’s 8GB on the 120GB edition, 6GB on the 250GB edition, and 12GB on the 512GB edition.
Also if you haven’t noticed already, the sequential writes on the Samsung 840 are on the slow side ranging from 130 MB/s to 330 MB/s depending on capacity. During a Q&A session at the Samsung SSD Summit, Samsung mentioned that the TLC NAND will be ~50% slower than MLC (2 bit per cell) NAND, but no exact details were given. That said, the specifications between the three drives suggest that the sequential write bottleneck is due to the TLC NAND since the increase of packages and/or dies per package will yield higher sequential write performance.
Samsung 830 vs Samsung 840 vs Samsung 840 Pro Specifications
|Samsung 830||Samsung 840||Samsung 840 Pro|
|Controller||Samsung S4LJ204X01-Y040||Samsung S4LN021X01-8030||Samsung S4LN021X01-8030|
|NAND||27nm Toggle Mode 1.0 MLC||21nm Toggle Mode 2.0 TLC||21nm Toggle Mode 2.0 MLC|
|Sequential Reads||520 MB/s||540 MB/s||540 MB/s|
|Sequential Writes||400 MB/s||250 MB/s||450 MB/s|
|Warranty||3 Years||3 Years||5 Years|
Comparing the 840 to the 830 and the 840 Pro, there are a few differences to note. First off, all three drives use different NAND. Whereas the 830 is using Samsung’s older 27nm MLC (2 bit per cell) NAND, the 840 Pro is using Samsung’s new 21nm MLC (2 bit per cell) NAND, and the 840 is using Samsung’s new 21nm TLC (3 bit per cell) NAND. Additionally, both the Samsung 840 and the Samsung 840 Pro are using faster Toggle 2.0 NAND, which is rated at up to 400 Mbits/s, which is significantly faster than Toggle 1.0 NAND, used in the Samsung 830, which is rated at up to 133 Mbits/s.
There’s also a difference in sequential read and write speeds here as well. Whereas sequential writes all top out at the 500+MB/s range, sequential writes on the Samsung 840 takes a significant dive coming in at only 250 MB/s.
Finally, there’s also the warranty as well. The Samsung 840 Pro receives an industry leading 5 year warranty whereas the 840 and 830 gets a more standard 3 year warranty. Let’s move on…