Original Link: http://www.anandtech.com/show/3656/corsairs-force-ssd-reviewed-sf1200-is-very-good

Update: Random write performance of the drive we reviewed may change with future firmware updates. Click here to find out more.

Corsair’s late entry into the SSD market meant that it missed the JMicron mess of the early days, but it also meant that Corsair missed the bulk of the early Indilinx boat. Not interested in making the same mistake twice, Corsair took the same risk as many other SSD makers and got in bed with a little company called SandForce.

Widely believed to be the creator of the technology behind Seagate’s first SSD, SandForce has been popping up all over the place lately. We first encountered the company late last year with a preview of OCZ’s Vertex 2 Pro. SandForce's technology seemed promising.

The problem of maintaining SSD performance is a lot like keeping a room tidy and clean. If you make sure to put things in the right place the first time and don’t let dirt accumulate, you’ll end up with an organized, pristine looking room. However if you just throw your stuff around and let stains go untouched, you’ll spend a lot more time looking for things and probably end up ruining the place.

The same holds true for SSDs. If the controller doesn’t properly place data it’ll take longer to place new data. And if the controller doesn’t properly wear level, you’ll end up reducing the life of the drive.

I’ve explained the how behind all of this countless times before, so I’ll spare you the details here. Needless to say, it’s a juggling act. One that requires a fast enough controller, a large amount of fast storage (whether it is on-die cache or off-chip DRAM) and a good algorithm for managing all the data that gets thrown at it.

At a high level Crucial/Micron, Indilinx and Intel take a relatively similar approach to the problem. They do the best with the data they’re given. Some do better than others, but they ultimately take the data you write to the drive and try to make the best decisions as to where to put it.

SandForce takes a different approach. Instead of worrying about where to place a lot of data, it looks at ways to reduce the amount of data being written. Using a combination of techniques akin to lossless data compression and data deduplication, SandForce’s controllers attempt to write less to the NAND than their competitors. By writing less, the amount of management and juggling you have to do goes down tremendously. SandForce calls this its DuraWrite technology.

DuraWrite isn’t perfect. If you write a lot of highly compressed or purely random data, the algorithms won’t be able to do much to reduce the amount of data you write. For most desktop uses, this shouldn’t be a problem however.

Despite the obvious achilles’ heel, SandForce’s technology was originally designed for use in the enterprise market. This lends credibility to the theory that SandForce was Seagate’s partner of choice for Pulsar. With enterprise roots, SandForce’s controllers and firmware are designed to support larger-than-normal amounts of spare area. As you may remember from our earlier articles, there’s a correlation between the amount of spare area you give a dynamic controller and overall performance. You obviously lose usable capacity, but it helps keep performance high. SandForce indicates that eventually we’ll see cheaper consumer drives with less NAND set aside as spare area, but for now a 128GB SandForce drive only gives you around 93GB of actual storage space.

Introducing the SF-1200

The long winded recap brings us to our new friend. The Vertex 2 Pro I previewed last year used a full fledged SF-1500 implementation, complete with ridiculously expensive supercap on board. SandForce indicated that the SF-1200 would be more reasonably priced, at the expense of a performance hit. In between the two was what we got with OCZ’s Vertex Limited Edition. OCZ scored a limited supply of early controllers that didn’t have the full SF-1500 feature set, but were supposedly better than the SF-1200.

Today we have Corsair’s Force drive, its new performance flagship based on the SF-1200. Here’s what SandForce lists as the differences between the SF-1500 and SF-1200:

SandForce Controller Comparison
  SF-1200 SF-1500
Flash Memory Support MLC MLC or SLC
Power Consumption 550 mW (typical) 950 mW (typical)
MTTF 2,000,000 operating hours 10,000,000 operating hours
Reliability 5 year customer life cycle 5 year enterprise life cycle


The Mean Time To Failure numbers are absurd. We’re talking about the difference between 228 years and over 1100 years. I’d say any number that outlasts the potential mean time to failure of our current society is pretty worthless. Both the SF-1200 and SF-1500 are rated for 5 year useful lifespans, the difference is that SandForce says the SF-1200 can last for 5 years under a "customer" workload vs. an enterprise workload for the SF-1500. Translation? The SF-1500 can handle workloads with more random writes for longer.

The SF-1500 also appears to be less error prone, but that’s difficult to quantify in terms of real world reliability. The chip sizes are identical, although the SF-1500 draws considerably more power. If I had to guess I’d say the two chips are probably the same with the differences amounting to be mostly firmware, binning and perhaps fusing off some internal blocks. Maintaining multiple die masks is an expensive task, not something a relative newcomer would want to do.

Note the lack of any external DRAM. Writing less means tracking less, which means no external DRAM is necessary.

Regardless of the difference, the SF-1200 is what Corsair settled on for the Force. Designed to be a high end consumer drive, the Force carries a high end price. Despite it’s 100GB capacity there’s actually 128GB of NAND on the drive, the extra is simply used as spare area for block recycling by the controller. If we look at cost per actual GB on the drive, the Force doesn’t look half bad:

SandForce Controller Comparison
Drive NAND Capacity User Capacity Drive Cost Cost per GB of NAND Cost per Usable GB
Corsair Force 128GB 93.1GB $410 $3.203 $4.403
Corsair Nova 128GB 119.2GB $369 $2.882 $3.096
Crucial RealSSD C300 256GB 238.4GB $680 $2.656 $2.852
Intel X25-M G2 160GB 149.0GB $489 $3.056 $3.282
OCZ Vertex LE 128GB 93.1GB $394 $3.078 $4.232


But looking at cost per user addressable GB isn’t quite as pretty. It’s a full $1.12 more per GB than Intel’s X25-M G2. It's also a bit more expensive than OCZ's Vertex LE, although things could change once Corsair starts shipping more of these drives.

Power - A Telling Story








The Test

Motherboard: Intel DX58SO (Intel X58)
Chipset: Intel X58 + Marvell SATA 6Gbps PCIe
Chipset Drivers: Intel + Intel IMSM 8.9
Video Card: eVGA GeForce GTX 285
Video Drivers: NVIDIA ForceWare 190.38 64-bit
Desktop Resolution: 1920 x 1200
OS: Windows 7 x64

Sequential Read/Write Speed

Using the 6-22-2008 build of Iometer I ran a 3 minute long 2MB sequential test over the entire span of the drive. The results reported are in average MB/s over the entire test length:


I'll go ahead and ruin the surprise right now - in the synthetic tests, you can't tell the difference between the Vertex LE and Corsair's Force drive. The two are identical performers. And it's not a bad thing, because they're both among the best.

2MB Sequential Write - MB/s

2MB Sequential Read - MB/s

Random Read/Write Speed


I've had to run this test two different ways thanks to the way the newer controllers handle write alignment. Without a manually aligned partition, Windows XP executes writes on sector aligned boundaries while most modern OSes write with 4K alignment. Some controllers take this into account when mapping LBAs to page addresses, which generates additional overhead but makes for relatively similar performance regardless of OS/partition alignment. Other controllers skip the management overhead and just perform worse under Windows XP without partition alignment as file system writes are not automatically aligned with the SSD's internal pages.

First up is my traditional 4KB random write test, each write here is aligned to 512-byte sectors, similar to how Windows XP might write data to a drive:

Update: Random write performance of the drive we reviewed may change with future firmware updates. Read here to find out more.

4KB Random Write - MB/s

Again, we have the Force and Vertex LE running shoulder to shoulder. The situation doesn't change at all when we look at 4K aligned writes (similar to how Windows 7/OS X 10.5/6 would behave):

4K Aligned - 4KB Random Write - MB/s

4KB Random Read - MB/s

Random read speed rounds out our tests and shows us no difference between the SF-1200 and earlier SF-1500 derived SSDs.

Overall System Performance using PCMark Vantage


PCMark Vantage - Overall Suite

Real world performance is very competitive. Corsair's Force is easily in the top 3 for best performing SSDs on the market today.


PCMark Vantage - Memories Test


PCMark Vantage - TV & Movies Test


PCMark Vantage - Gaming Test


PCMark Vantage - Music Test


PCMark Vantage - Communications Test


PCMark Vantage - Productivity Test


PCMark Vantage - HDD Test

AnandTech Storage Bench

Note that our 6Gbps controller driver isn't supported by our custom storage bench here, so the C300 results are only offered in 3Gbps mode.





AnandTech Storage Bench - Light Workload

I've always loved the performance of SandForce's controllers, I've just been worried about their reliability. While we wait for the latter to prove itself over time, the performance is very good today. The Corsair Force is very competitive, as fast as any other SF drive and faster than nearly all other SSDs.



AnandTech Storage Bench - Heavy Workload

Once again, very little difference between Corsair's Force and OCZ's Vertex LE. SandForce's performance isn't as strong in our heavy downloading workload, the Corsair Nova (with the latest Indilinx firmware) actually does better.


AnandTech Storage Bench - Gaming Workload

Here we're completely bound by read performance. I'm afraid the only way you'll get faster is via RAID or a 6Gbps controller in Crucial's case.

TRIM Performance

The SF-1200 fully supports TRIM and to test it out I peppered the Corsair Force drive with random writes and used HD Tach to look at sequential read/write speed across all LBAs of the used drive.

Remember we should be seeing sequential read/write performance of around 265/251 MB/s:

Performance is down, as you'd expect, but not to unbearable levels and it's also pretty consistent. While most drives will have worse write performance than read performance, if you look closely you'll see that read speed falls further than write speed. Perhaps all of the tracking overhead is making calculating and retrieving data more difficult? Remember that you can't just read data back from the SF drive since the full data isn't stored, you have to perform math on the stored data to retrieve what was actually written.

I then TRIMed the entire contents of the drive and re-ran the test:

Performance looks better. It's not at peak performance yet (~78% of peak read speed, 93% of peak write speed) but TRIM appears to be working relatively aggressively. The SandForce controller is very resilient, especially when combined with TRIM. My only concern continues to be long term reliability of these drives.

Final Words


Well, so much for the SF-1200 being a slouch. From the looks of it, I'd say that what you're looking at is a binned SF-1500 that performs well enough for most client use. Corsair's Force delivers the exact same performance as OCZ's Vertex LE, which also makes it your best bet if you're looking for a single drive that offers better-than-Intel performance. Unfortunately you do pay for it. If you look at how much you're paying per usable GB of space, these SandForce drives carry a ~33% price premium over Intel's X25-M G2.

The Corsair Force drive should be resilient enough to maintain good performance regardless of desktop workload. SandForce's unique architecture means that read performance actually suffers more than write performance over time, thankfully you'll never be in a situation where you'll need to read back LBAs that have garbage data in them so this shouldn't be a problem.

I really have no performance complaints about the SF-1200 or Corsair's Force drive. Both did very well in our tests. My concerns continue to be about long term reliability since we've only really seen these drives shipping in earnest for a couple of months now. If you're fine taking the risk, the performance is very nice. Otherwise I'd wait to see how these drives hold up over time before committing.

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