Original Link: http://www.anandtech.com/show/6388/intel-ssd-335-240gb-review



Introduction

Back in February, Intel released its first SandForce based SSD: the Intel SSD 520. Since then Intel's SSD lineup has evolved. A couple of months after the 520's release, Intel released a more mainstream focused SSD 330. Architecturally the SSD 520 and 330 were the same as both used SandForce's SF-2281 controller and IMFT's MLC NAND. The only real differences were limited to NAND quality and firmware; the 520 used higher binned NAND with more P/E cycles and its firmware was also more finely tuned to provide better performance.

While SandForce has yet to release its 3rd generation SSD controller, there's still room to upgrade one major component of these drives: the NAND itself. IMFT (Intel's and Micron's NAND joint-venture) has been fairly open about its next generation NAND products, including the transition to 20nm MLC NAND. Moving to smaller process geometries decreases die area, which increases the number of NAND die that can be produced on a single wafer (or increases the capacity that can reliably be produced on a single die). The move to 20nm is a necessary part of continuing to drive SSD costs down, although as with all process transitions we won't see those cost savings initially (die savings are offset by higher costs of a new process at the start).

IMFT's 20nm announcement happened back in April 2011. At the time, we were told not to expect to see 64Gb 20nm MLC NAND devices in SSDs until the middle of 2012. Now, a year and a half later, production is finally at a stage where volume and yields are both high enough for an actual product release. The vehicle for introduction? Intel's SSD 335.

As the name already suggests, the 335 is not a major upgrade over the 330. Intel usually reserves XX0 product names for bigger upgrades, such as the SSD 520 update where Intel moved to SandForce from a Marvell controller that was used in the SSD 510. The more minor updates (usually NAND die shrinks) only change the last number of the model. In other words, SSD 335 is essentially the SSD 330 but with 20nm MLC NAND instead of 25nm MLC NAND. Below is a full comparison of Intel's current consumer SSDs:

Comparison of Intel's Consumer SSDs
  SSD 330 (240GB) SSD 335 (240GB) SSD 520 (240GB)
Capacities (GB) 60, 120, 180, 240 240 60, 120, 180, 240, 480
Controller SandForce SF-2281
NAND Intel 25nm MLC Intel 20nm MLC Intel 25nm MLC
Sequential Read 500MB/s 500MB/s 550MB/s
Sequential Write 450MB/s 450MB/s 520MB/s
4KB Random Read 42K IOPS 42K IOPS 50K IOPS
4KB Random Write 52K IOPS 52K IOPS 80K IOPS
Warranty 3 years 3 years 5 years

At first, the SSD 335 will only be available in a 240GB capacity. I suspect that this has to do with 20nm NAND yields and volumes; it's a new process, yields are obviously lower and Intel hasn't had time to build an enormous stock yet. By only releasing a 240GB model at this point, which Intel tells us is the most popular capacity, it makes sure the 240GB model should be available in sufficient volume for the holiday market. If Intel had released all capacities simultaneously, it's possible that some capacities would have ran out of stock quickly. Intel likely still has a decent stock of 25nm NAND, so the 330 will stick around for at least a few months while the 335 ramps up additional capacities. The Intel SSD 520 will still be available as well, although I'm hearing that its successor is coming soon.

In terms of performance, the SSD 330 and SSD 335 are similar. This isn't shocking given that they are both based on the same controller and the only difference is the move from 25nm to 20nm MLC NAND. We aren't going to see any significant improvements in SandForce based SSDs until the third generation (SF-3000) controllers become available, which should be some time next year. There have of course been minor modifications to the firmware to support 20nm MLC NAND.

Similar to the SSD 330, the SSD 335 comes with a desktop installation kit including a 2.5" to 3.5" adapter, SATA cable and a Molex to SATA power adapter. 

NewEgg Price Comparison (10/29/2012)
Capacity 60/64GB 120/128GB 240/256GB 480/512GB
Intel SSD 335 N/A N/A $184 (MSRP) N/A
Intel SSD 330 $70 $99 $190 N/A
Intel SSD 520 $95 $120 $240 $490
Crucial m4 $75 $110 $200 $390
Samsung SSD 830 $100 $85 $170 $530
Samsung SSD 840 N/A $110 $200 $450
Plextor M5S $65 $120 $200 N/A
OCZ Vertex 4 $75 $100 $200 $400
Corsair Neutron N/A $130 $220 N/A

Intel's target with the SSD 330 was to bring an affordable drive to the market and the SSD 335 continues this trend. Suggested retail price of $184 for a 240GB drive is very competitive and there aren't many drives that can beat that at the moment. 

Update: The 240GB SSD 335 is already available in NewEgg for $210, which is unfortunately over $20 more than what the MSRP suggested.

The NAND

Intel's 20nm MLC NAND is mostly the same as its 25nm MLC NAND. We are still looking at 8GB per die with an 8KB page size, although Intel does have a 16GB die in development which will also increase the page size to 16KB. Since the key aspects are the same, there haven't been any dramatic changes to performance. Intel wouldn't provide us with any specific numbers but program latency is the same and erase time is slightly longer than its 25nm MLC NAND.

The new NAND also enables ONFI 2.3 support. ONFI 2.3 doesn't bring any bandwidth improvements as the spec still maxes out at 200MB/s. IMFT's 16GB die will feature ONFI 3.0 support, bringing the maximum bandwidth between the controller and NAND to 400MB/s per channel. The biggest new feature in ONFI 2.3 is support for the EZ-NAND protocol, although Intel has not adopted this protocol to its NAND. EZ-NAND allows ECC to be offloaded from the SSD controller to a separate controller (can be integrated into the NAND package as well):

Normal NAND on the left - EZ-NAND on the right

The advantage of offloading the ECC from the controller is that now ECC can be updated along with NAND without the need for a new controller. ECC is strictly implemented in hardware, which means a firmware update doesn't help; you will need a new physical controller to update ECC. As we move to smaller process nodes, the need for ECC increases as the error rate goes up. With more error prone NAND, it becomes even more important to decouple ECC generations from the host controller since the same controller can be used for more than one NAND generation. In the Intel SSD 335, ECC is still handled by the SF-2281 controller but in theory, manufacturers using Intel NAND could implement a third party off-chip ECC controller in their SSDs.



Testing Endurance

We've mentioned in the past that NAND endurance is not an issue for client workloads. While Intel's SSD 335 moves to 20nm MLC NAND, the NAND itself is still still rated at the same 3,000 P/E cycles as Intel's 25nm MLC NAND. Usually we can't do any long-term endurance testing on SSDs for the initial review because it simply takes way too long to wear out an SSD. Even if you're constantly writing to a drive, it will take weeks, possibly even months for the drive to wear out. Fortunately Intel reports total NAND writes and percentage of lifespan remaining as SMART values that can be read using the Intel SSD Toolbox. The variables we want to pay attention to are the E9 and F9 SMART values, which represent the Media Wearout Indicator (MWI) and total NAND writes. Using those values, we can estimate the long-term endurance of an SSD without weeks of testing. Here is what the SMART data looked like before I started our endurance test:

This screenshot was taken after all our regular tests had been run, hence there are already some writes to the drive, although nothing substantial. What surprised me was that the MWI was already at 92, even though I had only written 1.2TB to the NAND. Remember that the MWI begins at 100 and then decreases down to 1 as the drive uses up its program/erase cycles. Even after it has hit 1, it's likely the drive can still withstand additional write/erase cycles thanks to MLC NAND typically behaving better than the worst-case estimates.

We've never received an Intel SSD sample that started with such a low MWI, indicating either a firmware bug or extensive in-house testing before the drive was sent to us.

To write as much as possible to the drive before the NDA lift, I first filled the drive with incompressible data and then proceeded with incompressible 4KB random writes at queue depth of 32. SandForce does real-time data compression and deduplication, so using incompressible random data was the best way to write a lot of data to NAND in a short period of time. I ran the tests in about 10-hour blocks, here is the SMART data after 11 hours of writing:

I had written another ~3.8TB to the NAND in just 11 hours but what's shocking is that the MWI had dropped from 92 to 91. With the SSD 330, Anand wrote 7.6TB to the NAND and the MWI stayed at 100, and that was a 60GB model; our SSD 335 is 240GB and thus it should be more durable (more NAND to write to). It's certainly possible that the MWI was at the edge of 92 and 91 after Intel's in-house testing, but I decided to run more tests to see if that was the case. Let's fast-forward 105 hours that I spent writing to the drive in total:

In a few days, I managed to write a total of 37.8TB to the NAND and during that time, the MWI had dropped from 92 to 79. In other words, I used up 13% of the drive's available P/E cycles. This is far from being good news. Based on the data I gathered, the MWI would hit 0 after around 250TB of NAND writes, which translates to less than 1,000 P/E cycles.

I showed Intel my findings and they were as shocked as I was. The drive had undergone their validation before shipping and nothing out of the ordinary was found. Intel confirmed that the NAND in SSD 335 should indeed be 3,000 P/E cycles, so my findings contradicted with that data by a fairly significant margin. Intel hadn't seen anything like this and asked me to send the drive back for additional testing. We'll be getting a new SSD 335 sample to see if we can replicate the issue.

It's understandable that the endurance of 20nm NAND may be slightly lower compared to 25nm even though they are both rated at 3,000 P/E cycles (Intel does have 25nm with 5,000 cycles as well) because 25nm is now a mature process whereas 20nm is very new. Remember that the P/E cycle rating is the minimum the NAND must withstand; in reality it can be much more durable as we saw with the SSD 330 (based on our tests its NAND was good for at least 6,000 P/E cycles). Hence both 20nm and 25nm MLC NAND can be rated at 3,000 cycles, although their endrudance in real world may vary (but both should still last for at least 3,000 cycles). 

It's too early to conclude much based on our sample size of one. There's always the chance that our drive was defective or subject to a firmware bug. We'll be updating this section once we get a new drive in house for additional testing.



Inside the Intel SSD 335

Similar to the SSD 330, the SSD 335 has a single thermal pad covering the controller. The whole case is made out of metal, so heat dissipation in general should not be an issue. There doesn't seem to be any visible differences between the PCBs of SSD 335 and 330, other than the fact that the SSD 335 loses the "BIN 2" sticker and is manufactured in fab 4 instead of fab 3 (although it's completely possible that SSD 335s are manufactured in fab 3 as well). 

The SF-2281

As usual, there are a total of sixteen NAND packages, eight on each side of the PCB. Each NAND package consists of two 8GB 20nm MLC NAND dies, making each NAND package 16GB in capacity. The new 20nm process node is indicated by the 12th character, which is an F. Process nodes follow the alphabet, meaning that F is 20nm, E is 25nm, D is 34nm and so on. 

Test System

CPU

Intel Core i5-2500K running at 3.3GHz (Turbo and EIST enabled)

Motherboard

AsRock Z68 Pro3

Chipset

Intel Z68

Chipset Drivers

Intel 9.1.1.1015 + Intel RST 10.2

Memory G.Skill RipjawsX DDR3-1600 2 x 4GB (9-9-9-24)
Video Card XFX AMD Radeon HD 6850 XXX
(800MHz core clock; 4.2GHz GDDR5 effective)
Video Drivers AMD Catalyst 10.1
Desktop Resolution 1920 x 1080
OS Windows 7 x64

 



Random Read/Write Speed

The four corners of SSD performance are as follows: random read, random write, sequential read and sequential write speed. Random accesses are generally small in size, while sequential accesses tend to be larger and thus we have the four Iometer tests we use in all of our reviews.

Our first test writes 4KB in a completely random pattern over an 8GB space of the drive to simulate the sort of random access that you'd see on an OS drive (even this is more stressful than a normal desktop user would see). I perform three concurrent IOs and run the test for 3 minutes. The results reported are in average MB/s over the entire time. We use both standard pseudo randomly generated data for each write as well as fully random data to show you both the maximum and minimum performance offered by SandForce based drives in these tests. The average performance of SF drives will likely be somewhere in between the two values for each drive you see in the graphs. For an understanding of why this matters, read our original SandForce article.

Desktop Iometer - 4KB Random Read (4K Aligned)

Random read performance has never been SandForce's biggest strength and even Intel couldn't massively improve it with its own firmware. The SSD 335 is in fact slower than the SSD 330 here.

Desktop Iometer - 4KB Random Write (4K Aligned) - 8GB LBA Space

Desktop Iometer - 4KB Random Write (8GB LBA Space QD=32)

Random write speed at small queue depths is also slower compared to the 520 and 330, although at queue depth of 32 the difference is negligible. 

Sequential Read/Write Speed

To measure sequential performance I ran a 1 minute long 128KB sequential test over the entire span of the drive at a queue depth of 1. The results reported are in average MB/s over the entire test length.

Desktop Iometer - 128KB Sequential Read (4K Aligned)

Desktop Iometer - 128KB Sequential Write (4K Aligned)

Sequential read performance is identical to SSD 330, but sequential write speed is slightly slower. What's notable is sequential write performance with incompressible data: the Intel SSD 335 manages to beat both the 520 and Corsair's Force GS by a noticeable margin.



AS-SSD Incompressible Sequential Performance

The AS-SSD sequential benchmark uses incompressible data for all of its transfers. The result is a pretty big reduction in sequential write speed on SandForce based controllers, while other drives continue to work at roughly the same speed as with compressible data.

Incompressible Sequential Read Performance - AS-SSD

Incompressible Sequential Write Performance - AS-SSD

As the IOmeter tests in the previous page hinted, the 335 is a good performer with incompressible data. Incompressible sequential write speed is the highest we have ever tested on a SandForce drive. Compared to the SSD 330, the performance advantage is roughly 50% and still over 10% comared tp the 520.



Performance vs. Transfer Size

ATTO is a great tool for quickly testing sequential performance at multiple transfer sizes. Surprisingly the SSD 335 is slightly behind SSD 520 and 330 in both read and write speeds. Small file read performance isn't very good with only the 320 coming in slower, though small IO reads have always been bad on SandForce drives. Fortunately write speeds are much better since ATTO uses highly compressible data.



AnandTech Storage Bench 2011

Last year we introduced our AnandTech Storage Bench, a suite of benchmarks that took traces of real OS/application usage and played them back in a repeatable manner. Anand assembled the traces out of frustration with the majority of what we have today in terms of SSD benchmarks.

Although the AnandTech Storage Bench tests did a good job of characterizing SSD performance, they weren't stressful enough. All of the tests performed less than 10GB of reads/writes and typically involved only 4GB of writes specifically. That's not even enough exceed the spare area on most SSDs. Most canned SSD benchmarks don't even come close to writing a single gigabyte of data, but that doesn't mean that simply writing 4GB is acceptable.

Originally we kept the benchmarks short enough that they wouldn't be a burden to run (~30 minutes) but long enough that they were representative of what a power user might do with their system. Later, however, we created what we refer to as the Mother of All SSD Benchmarks (MOASB). Rather than only writing 4GB of data to the drive, this benchmark writes 106.32GB. This represents the load you'd put on a drive after nearly two weeks of constant usage. And it takes a long time to run.

1) The MOASB, officially called AnandTech Storage Bench 2011—Heavy Workload, mainly focuses on the times when your I/O activity is the highest. There is a lot of downloading and application installing that happens during the course of this test. Our thinking was that it's during application installs, file copies, downloading, and multitasking with all of this that you can really notice performance differences between drives.

2) We tried to cover as many bases as possible with the software incorporated into this test. There's a lot of photo editing in Photoshop, HTML editing in Dreamweaver, web browsing, game playing/level loading (Starcraft II and WoW are both a part of the test), as well as general use stuff (application installing, virus scanning). We included a large amount of email downloading, document creation, and editing as well. To top it all off we even use Visual Studio 2008 to build Chromium during the test.

The test has 2,168,893 read operations and 1,783,447 write operations. The IO breakdown is as follows:

AnandTech Storage Bench 2011—Heavy Workload IO Breakdown
IO Size % of Total
4KB 28%
16KB 10%
32KB 10%
64KB 4%

Only 42% of all operations are sequential; the rest ranges from pseudo to fully random (with most falling in the pseudo-random category). Average queue depth is 4.625 IOs, with 59% of operations taking place in an IO queue of 1.

Many of you have asked for a better way to really characterize performance. Simply looking at IOPS doesn't really say much. As a result we're going to be presenting Storage Bench 2011 data in a slightly different way. We'll have performance represented as Average MB/s, with higher numbers being better. At the same time we'll be reporting how long the SSD was busy while running this test. These disk busy graphs will show you exactly how much time was shaved off by using a faster drive vs. a slower one during the course of this test. Finally, we will also break out performance into reads, writes, and combined. The reason we do this is to help balance out the fact that this test is unusually write intensive, which can often hide the benefits of a drive with good read performance.

There's also a new light workload for 2011. This is a far more reasonable, typical every day use case benchmark. It has lots of web browsing, photo editing (but with a greater focus on photo consumption), video playback, as well as some application installs and gaming. This test isn't nearly as write intensive as the MOASB but it's still multiple times more write intensive than what we were running last year.

We don't believe that these two benchmarks alone are enough to characterize the performance of a drive, but hopefully along with the rest of our tests they will help provide a better idea. The testbed for Storage Bench 2011 has changed as well. We're now using a Sandy Bridge platform with full 6Gbps support for these tests.

AnandTech Storage Bench 2011—Heavy Workload

We'll start out by looking at average data rate throughout our new heavy workload test:

Heavy Workload 2011 - Average Data Rate

The SSD 335 performs very well in our Heavy suite. It's on-par with most high-end SSDs and even manages to beat the 520 and 330. The improvement over the 330 is quite good.

Heavy Workload 2011 - Average Read Speed

Heavy Workload 2011 - Average Write Speed

The next three charts just represent the same data, but in a different manner. Instead of looking at average data rate, we're looking at how long the disk was busy for during this entire test. Note that disk busy time excludes any and all idles, this is just how long the SSD was busy doing something:

Heavy Workload 2011 - Disk Busy Time

Heavy Workload 2011 - Disk Busy Time (Reads)

Heavy Workload 2011 - Disk Busy Time (Writes)

 



AnandTech Storage Bench 2011—Light Workload

Our new light workload actually has more write operations than read operations. The split is as follows: 372,630 reads and 459,709 writes. The relatively close read/write ratio does better mimic a typical light workload (although even lighter workloads would be far more read centric).

The I/O breakdown is similar to the heavy workload at small IOs, however you'll notice that there are far fewer large IO transfers:

AnandTech Storage Bench 2011—Light Workload IO Breakdown
IO Size % of Total
4KB 27%
16KB 8%
32KB 6%
64KB 5%

Light Workload 2011 - Average Data Rate

Performance in our Light suite is as strong as it is in the Heavy suite; the SSD 335 is again faster than the 520 and 330.

Light Workload 2011 - Average Read Speed

Light Workload 2011 - Average Write Speed

Light Workload 2011 - Disk Busy Time

Light Workload 2011 - Disk Busy Time (Reads)

Light Workload 2011 - Disk Busy Time (Writes)

 



Performance Over Time & TRIM

SandForce has always exhibited strange behavior when it came to TRIM. Even Intel's custom firmware in the SSD 520 wasn't able to fix SandForce's TRIM problem. The issue happens when the SSD is completely filled with incompressible data (both user LBAs and spare area). Any performance degradation after that point won't be restored with a TRIM pass and instead will require a secure erase to return to new. I didn't expect the 335 to fix this but I still tortured the SSD 335 for 60 minutes, ran AS-SSD, TRIMed and reran AS-SSD:

Intel SSD 335 - Resiliency - AS SSD Sequential Write Speed - 6Gbps
  Clean After Torture (60min) After TRIM
Intel SSD 335 240GB 317.7MB/s 174.2MB/s 176.9MB/s

And the issues persists. This is really a big problem with SandForce drives if you're going to store lots of incompressible data (such as MP3s, H.264 videos and other highly compressed formats) because sequential speeds may suffer even more in the long run. As an OS drive the SSD 335 will do just fine since it won't be full of incompressible data, but I would recommend buying something non-SandForce if the main use will be storage of incompressible data.



Power Consumption

Idle power consumption has gone down thanks to smaller lithography NAND and possibly some firmware tweaks, but on the other hand load power consumption has gone up. The difference is fairly negligible with compressible data but the SSD 335 consumes a good 0.6W more than the 240GB SSD 520 when writing incompressible sequential data to it.

Drive Power Consumption - Idle

Drive Power Consumption - Sequential Write

Drive Power Consumption - Random Write



Final Words

The SSD 335 is mostly an incremental upgrade from the SSD 330. There are minor changes in performance that are mainly positive, but 20nm NAND is really the only new thing that the SSD 335 brings. It is always impressive to think about performance going up with subsequent NAND generations, especially since program/erase times typically get longer each generation (thus requiring more sophisticated controllers and firmware to offset the slower NAND). The 330 ended up being a very competitive value drive, and from a performance standpoint it looks like the 335 is poised to carry the torch forward. 

On the controller side, SandForce's SF-2281 is definitely getting a bit long in the tooth compared to the latest high-end competition but the performance it provides is still good enough for most client workloads. The upside of everyone ultimately being limited by 6Gbps SATA is that there isn't much of a performance push for newer controllers.

Intel has generally been our recommended brand when it comes to buying SandForce drives. The same will likely be true for the SSD 335 as well, however we're going to hold off on any final judgements until we get another sample in house so we can confirm at least somewhat similar endurance to the outgoing 330.

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