If you have been following ABT, you will notice that we let the cat out of the bag a few months ago when we posted the “Patriot Torqx M28 256 GB SSD Unboxing and Performance Preview” article. In there we gave you a look at the Solid State Disk (SSD) we have been testing for the past few weeks and a real world performance preview. In this article we will delve deeper into the underlying architecture of a Solid State Drive (SSD) and see what makes it tick.

Since we posted that article a few months ago, a lot has changed which was the reason for delaying this article. When I was originally ready to post the results, Patriot informed me that they were very close to releasing a new firmware for the SSD that would support TRIM command. I decided to delay the article and test the SSD again with the new firmware and post the new results as well.

Over the course of next few pages, I’ll try to explain as best I can what makes a SSD function, what is the underlying technology. We’ll see how data is written and read and then I will round it off with the benchmarks. I will try to keep the explanation as simple as possible, as I remember how empty I came away after the first time I tried to read the SSD technology due to the technical jargon. To make it easy on our readers so as to understand the working of the technology, I have made diagrams to explain the processes.

So the basic premise comes to this:

In the past few years while the CPU has been increasing in speed, one component that has not advanced at the same rate is the storage sub-system. While CPUs have evolved to process the data in nanoseconds, the time taken for accessing the data off of the hard disk drive is still measured in milliseconds. Although small in essence, it is still quite large compared to the time it takes for the CPU to process the data.

Eventually you may be running the latest brand spanking new 8-core processor in the near future with 2000 MHz DDR3, but the one thing that will be holding you back will still be your mechanical storage. As we found out in our Preview article, that the performance nearly doubled in some cases by just upgrading the storage system.

Let’s start by learning how a SSD works.

Meet the Cell

Before looking at the Flash Cell (or Transistor), let’s take a look at a MOSFET (Metal Oxide Field Effect Transistor). A MOSFET has three terminals: Source, Gate and Drain. When a positive charge is applied to the gate, the electrons from the p-type substrate get pulled towards it and form a thin channel below it. Think of this channel as a bridge that allows the electrons from the source to flow to the drain (MOSFET is on and stores a 1). When the positive voltage applied to the gate is taken away, the flow of electrons from source to drain stops (MOSFET is off and stores a 0). As computers store information in 0s and 1s, a MOSFET can only store 1s as long as external power is applied to its gate. Therefore, all the 1s will be turned into 0 as soon as external power is taken away, thereby causing loss of data.

Due to this reason, MOSFETs need to be modified before they can be used for storing data without the use of external power. Enter Flash Cell, which has an extra gate called the Floating Gate.

To program the cell, a high voltage is applied to the control gate. This voltage attracts the electrons and causes them to tunnel through the oxide layer and move into the Floating Gate. This changes the value of the cell to 0. If you remove the voltage applied to the gate, the electrons will stay in the floating gate and the cell will retain its value of 0. To erase the cell, apply the voltage across the channel with reversed polarity as before. The electrons are removed from the floating gate thereby changing the value of the cell to 1. Thus this cell can store two states, 1 or 0.

SLC vs MLC

There are two kinds of flash technologies in use today: Single-Level Cell (SLC) flash and Multi-Level Cell (MLC) flash. The key difference between the two is the amount of data one cell can store. SLC flash is capable of storing 1 bit per cell, unlike MLC flash which can store 2 bits per cell. Below is an image of a SLC chip and a MLC chip. If you look at them, they are indistinguishable and look the same from the outside. So, for effectively the same die area, MLC technology provides you with double the storage capacity.

SLC transistor has two states, 0 and 1. MLC flash transistor can have four states 00, 01, 10, 11. A 0 or 1 is determined by the threshold voltage V_t. This voltage is calculated by the amount of charge on the floating gate of the flash cell. For example when the threshold voltage is high enough, around 4.0 V, the cell will be read as programmed or 1. No charge or threshold voltage < 4.0 V will cause the cell to be read as erased. Now in MLC flash, you can have different threshold voltage levels and have them be read as different states, thereby being able to store more data. An example of different states in SLC and MLC flash is shown below

To better understand the difference between SLC and MLC flash, think of a cell as a glass of water. The SLC glass can have two levels, empty (erased or 1) and full (programmed or 0). MLC glass can have four levels: empty (Fully erased or 11), 1/3 full (Partially erased or 10), 2/3 full (Partially programmed or 01), and full (Fully programmed or 00).

As MLC has four levels, the read time of MLC flash is higher when compared to SLC. This is because the reading application has to take some extra time to determine the exact reading of the cell. Another advantage that SLC flash has over the MLC flash is in the endurance department. Usually the endurance of SLC flash is 10x more than MLC flash. Therefore SLC flash is used in solid state disks made for servers where reliability is of prime importance.

Now that we know how flash memory works at the low level, let’s look at how data is read, written and erased.

Read Data , Write Data

The most basic component of a flash memory chip is the flash cell, which we just covered. Group a few of these cells together; you will get a page which is 4 KB in size. A page is the smallest entity that is readable/writable in a SSD. Next, group 128 pages together to get a block which is the smallest entity that can be erased. Moving on with the grouping, 1024 of these blocks form a plane. Then these planes are grouped together to form a flash die.

The image below will help explain the concept of grouping further.

The main points to remember here are that

• 1 Plane -> 1024 Blocks
• 1 Block -> 128 Pages
• 1 Page -> several flash cells

In terms of size,

• 1 Page -> 4KB
• 1 Block -> 512 KB
• 1 Plane -> 512 MB

How data is written to the SSD

Remember we just talked about a page which is the smallest entity that you can write data to or read data from in a SSD. The size of the page is normally 4 KB in size. So you can read or write data to a SSD 4 KB at a time. Now things are about to get interesting. Although you can read/write 4 KB at a time, if you want to erase you have to do so 512 KB at a time. Remember, that 512 KB is a block. So you can read/write in pages but can only erase in blocks. Pay close attention to the text in bold, as I’m going to refer to it in a moment.

When a user deletes a file, the OS marks it as deleted and removes it from it’s memory of files that exist on the disk. In reality the file is not deleted on the disk. This is how most of the file recovery software work. The file is truly deleted when it is overwritten by another file.

In a SSD, although an OS will mark a file as deleted, the SSD controller has no idea that the file is deleted. The problem arises when you try to write a new file to a page that has been marked as deleted by the OS. Remember the bolded text above, this condition will cause the difference in how a file is overwritten in SSD vs Hard Disk Drive (HDD). While the sectors containing deleted files in hard disk can be overwritten, this is not possible in SSD. This is because to overwrite data in a SSD, you first need to erase the old data.

To get around having to erase data everytime you want to write, SSDs try to fill up all the available pages first. So even though your operating system may say you have such and such free space left, the SSD controller does not know about the deleted files. The end result is that it takes longer to write a file to a SSD than you would expect because the resident data has to be erased first. Take a look at the example below of how the actual write operation works in a SSD.

1. The user wants to write 8 KB (2 Pages) of data. The block has 2 pages that are marked as deleted by the OS, but data still exists on the physical media.

2. To write the new data these 2 pages will have to be erased first. So the entire contents of the block (512 KB) are copied to the SSD cache, where individual pages can be deleted.

3. The new data is written over the previously deleted pages in the SSD cache.

4. The entire data (512 KB) is written back from the memory to the block along with the new data.

Notice that just to write 8 KB, we had to first copy 512 KB into the memory, then we had to write 512 KB back to the block. This is why SSDs write speeds go down as more and more data is written to them. This is why newer SSDs are being released with a larger cache as it really helps in the write speeds. The Torqx M28 drive we are testing in this review features 128 MB of cache.

TRIM to the rescue

This is where TRIM comes in. Supporting OSes query the drive for its rotational speed, and if the returned value is 0, the OS identifies the drives as a SSD. Thus the OS enables the TRIM command for the drive when files are deleted from it. The TRIM command tells the SSD controller to delete the pages on the NAND flash block when the user deletes the data contained in the pages in the OS. The entire block containing the data is copied into the memory cache, then the block is erased. After this procedure, the data sans the data deleted by the user is written back to the block from the memory cache. This results in longer delete times, but allows the write performance to be like the drive in its new state. Look at the example below.

What if you can’t TRIM ?

Not all the drives and OSes support TRIM. Most of the manufacturers are coming out with firmware updates for their SSDs to add the TRIM support. You will also need a TRIM supporting OS like Windows 7 to reap the benefit of this feature. If you cannot use this feature, there is another way by which you can restore your drive to its peak performance. HDDErase is a freeware utility that securely erases data on hard drives using the security erase unit command built into the firmware of ATA and SATA drives. This utlilty will clear every page on the drive, restoring the performance to like-new state. This utility can be downloaded from here.

Meet the Patriot Torqx M28 256 GB SSD

Product Page

Features

• Available in 128GB and 256GB capacities
• Interface: SATA I/II
• Raid Support: 0, 1, 0+1
• 256GB and 128GB: Sequential Read: up to 220MB/s Sequential Write: up to 200MB/s
• 128MB DRAM Cache
• 3.5″ bracket included
• Shock Resistant: 1500G/0.5ms
• Vibration Resistant: 20G/10~2000Hz with 3 Axis
• Operating Consumption & Power:

  DC 5V
  <244mA
  1.2W

• Operating Temperature: 0°C~70°C Storage Temperature: -55°C~ 95°C
• MTBF: >1,000,000 Hours
• Data Retention: 5 years at 25°C Data Reliability: Built in BCH 8, 12 and 16-bit ECC
• O/S Support: Windows® XP and Vista® Linux, and Mac OS X®
• Dimensions: 99.88 x 69.63x 9.3 mm
• Weight: 91g
• Certification: FCC/CE/RoHS
• 10 Year Warranty

This drive features 128 MB of cache which should help in the write performance as we discussed earlier and saw how important a large cache is while writing or deleting a file. The inclusion of a 3.5 inch adapter for mounting in the normal HDD slots in your case is a welcome addition. This SSD comes with an industry leading 10 year warranty, which should be plenty. The drive uses a Samsung controller.

Let’s look at the performance and why you should invest in a SSD.

Test System

• Intel Q9450 @ 3.2 GHz
• GIGABYTE EX-38 DS4 F5 BIOS
• GEIL 4 GB ( 2x 2GB ) Dual Channel RAM @ 800 MHz
• Visiontek ATI Radeon HD 4870
• Windows 7 Ultimate x64
• Intel Chipset Device Software Version: 9.1.1.1019
• ATI Catalyst 9.12

Synthetic Tests

• HDTune 3.50
• HDTach 3.0.4
• CrystalDiskMark 2.2
• ATTO Disk Benchmark 2.34
• PCMark Vantage HDD Test Suite

Real World Tests

• Crysis Warhead game folder copy folder to the same drive
• Crysis Warhead Ambush Level Load
• Muxing 7 video files to form one 2.18 GB file

Test Notes – The Abbreviations used on the images are explained below.

SSD New – Test done on the SSD in new state.

SSD Used – Test done on the SSD after filling every page on it.

SSD w/TRIM – New firmware installed on the disk which supports TRIM command.

HDD – The Seagate 7200.12 hard disk drive tested here.

ATTO Disk Benchmark 2.34

ATTO is one of the oldest hard drive benchmarks. It measures both read and write speeds and outputs the data in an easily readable graph. This test was run with default settings:

Right off the bat, the Patriot SSD offers exceptionally fast read and write speeds. The SSD offers around 220 MB/s of read speed in 8 KB blocks compared to Seagate HDD’s nearly 130 MB/s the  does. It will be interesting to see the effect in our real world tests. Notice the drop in speeds of a fully used SSD here as I explained earlier in the article why they occur. Read speeds remain unaffected, but write speeds suffer a hit of around 40-60 MB/s.

CrystalDiskMark 2.2

CrystalDiskMark is a HDD benchmark utility for your hard drive that enables you to measure sequential and random read/write speeds.

Here are some key features of “CrystalDiskMark”:

· Sequential reads/writes

· Random 4KB/512KB reads/writes

The blistering read and write performance continues here. This test doesn’t show the drop in speeds with a used SSD. This is one of the reasons the synthetic tests do not represent a real world scenario and why we test with real world files later in this article. But compare the 4K read and write performance of a SSD to HDD. The read performance is almost 22 times faster while the write performance is nearly 4.5 times faster. This gain in performance in seen booting of Windows as a SSD will load the small sized files a lot faster than a HDD.

HD Tune 3.50

HD Tune is a hard disk utility which has the following functions:

• Benchmark: measures the raw performance
  • Transfer Rate
  • Access Time
  • CPU Usage
  • Burst Rate
  • Random Access test
  • Write benchmark
• Hard Disk information which includes partition information, supported features, firmware version, serial number, disk capacity, buffer size, transfer mode
• Hard Disk Health
  • S.M.A.R.T. Information (Self-Monitoring Analysis and Reporting Technology)
  • Power On Time
• Error scan
• Temperature display

We are using the default setting of 64KB blocks for testing which might result in different results from other benchmarks as you will see in the write tests with a used SSD.

Read Test

Read performance of the used SSD takes a hit more than what was observed in the previous benchmarks but it is still faster than a HDD. Compare the access times of a SSD to those of HDD. It only takes 0.1ms on a new SSD to access a file while it takes 14.1ms to access a file on one of the fastest HDDs in the market. This is what is called responsiveness of your computer. When you launch an application on a HDD, it takes 14.1 ms for the HDD to access the files to launch the application. 14.1ms may not seem much, but having an application like Photoshop that loads all the brushes and plugins at start up, that little 14.1ms can amount to a lot of seconds. With a SSD and an access time of only 0.1s, any file in any page on the drive can be accessed almost instantly leading to faster load times.

Write Test

The SSD shows completely unacceptable performance scoring only 6.4 MB/s average. (Note: The test was done with 64KB blocks, so this is not representative of transfer speeds of all sized files.) Otherwise, the SSD is faster than the HDD on writes and access time is really really low. The performance is regained with the new TRIM supporting firmware.

Random Read Test

The Patriot SSD shows a low access time across a variety of file sizes compared to a HDD. Also compare the IOPS (Input/Output Operations Per Second) of a SSD to HDD. While a SSD can do nearly 13000 512 bytes IOPS, a HDD can only manage 70.

Random Write Test

Once again the SSD shows horrible performance in used state. It only manages 6 write IOPS and access time has ballooned to 155ms compared to 65 IOPS and 15ms in new state. But once the firmware supports TRIM, all is well and helps maintain like new performance.

File Benchmark test

Write speeds are affected in used state, but the new firmware recovers the speed.

HDTach 3.0.4

HD Tach is a low level hardware benchmark for random access read/write storage devices such as hard drives, removable drives (ZIP/JAZZ), flash devices, and RAID arrays. HD Tach uses custom device drivers and other low level Windows interfaces to bypass as many layers of software as possible and get as close to the physical performance of the device possible.

Once again used SSD write speed is all over the place, but the new firmware helps in recovering the speed.

PCMark Vantage HDD Test Suite

The HDD Test suite in PCMark Vantage consists of the following 8 tests

• HDD 1- Windows Defender
• HDD 2- Game HDD
• HDD 3- Importing pictures
• HDD 4- Windows Vista start-up
• HDD 5- Video editing
• HDD 6- Media Center
• HDD 7- Adding music to Windows Media Player
• HDD 8- Application loading

PCMark Vantage test results show a great increase in performance when upgrading from a HDD to a SSD. PCMark rates the performance of the SSD with TRIM support to be better than the SSD in new condition without TRIM support.

Crysis Warhead Game Folder copy folder to the same drive

In this test I install the Crysis Warhead game to the drive being benchmarked. Then I copy that game folder to another folder on the same drive using Microsoft’s Robocopy GUI and output the time taken. This benchmark will test both the read and the write speeds of the drive at the same time. I choose Crysis Warhead for this purpose as this game has a lot of files of various sizes. This should test the hard disk transfer speeds across vast sizes of files and mimic a real world scenario.

The game was patched with the 1.1 and 1.1 hotfix patch which introduces the 64-bit executable. The test is performed 3 times and the results averaged.

The transfer time is reduced to almost half with a SSD. This test should accurately represent a real world scenario where you copy files, so you can expect performance to be nearly doubled with a SSD over a HDD.

Crysis Warhead Ambush Level Load

Crysis Warhead 64-bit was used for this test. In this benchmark, I loaded up a save game on the first level of the game. The time taken to load the level can be seen in the console, which can be accessed by ‘~’ key. Here is a screen demonstrating an example.

We see a reduction of nearly 12s in load time with a SSD over a HDD. This is not as great as the previous test, but waiting 12s less for a level to load can’t be bad.

Video Muxing Test

This test represents the scenario where you may need to combine two separate video files or combine various audio and video streams to form one video file. The people who do a lot of video encoding go through this often in their day to day computing.

The videos used here are various trailers obtained from Divx7 Showcase page and “Just HD” section of Apple’s trailers webpage. Seven 1080p Full-HD video files were used in this test. The list along with size is shown below.

This test again nearly doubles the performance which goes to show how benefit if having a SSD in the system.

Conclusion

Money no object, if I were to recommend one upgrade in any system, it will most definitely be a SSD. Offering nearly double the performance over the fastest hard drive I have ever tested speaks volumes about the performance that a SSD delivers. Even a new GPU or CPU generation doesn’t always deliver double the performance of the last generation.

From here on, having the fastest system means having an SSD in there running the operating system in addition to other top end CPUs and GPUs and other hardware. Not only will the SSD make your system more responsive over a HDD, it will also give you bragging rights of having something that many others don’t. Which leads me to one of the problems with SSDs. With the current high cost of SSDs, they fill a niche in the consumer market. Not everyone will be itching to shell out nearly $700 for a 256 GB drive when you can acquire a 1 TB HDD for nearly $75-90 these days. However if you can scrounge up enough money to buy a SSD to load your OS, you will not regret the decision. With a limited budget, you should own a small SSD for your OS drive and HDD for storage purposes.

Then, there is the problem of losing performance when the SSD gets used. Not all SSDs and OSes out there support the TRIM command. But we are hearing good news in regards to TRIM support, with more and more manufacturers releasing TRIM supporting firmware. I expect SSDs shipping in the future to ship with a TRIM supporting firmware. On the OS side, good news is that Windows 7 supports this feature. This should relieve the user from the worries of losing performance on a SSD if they are running a SSD that supports TRIM on Windows 7.

For those of you, who might not have looked over the test results on previous page and only wanted to read the conclusion watch the video below to see the tests in action and why I so highly recommend a SSD.

A TRIM supporting firmware has now been released for this drive and can be downloaded from here http://www.patriotmem.com/support/firmwarep.jsp

Patriot Torqx M28 256GB SSD

Pros

• Industry leading 10 year warranty
• 128 MB of cache
• Fast speeds
• TRIM support

Cons

• Price ($745 at the time of the writing of this article)

In the end I can only think of two awards that do justice to this product.

«1. Introduction2. Meet the Cell, Types of Flash3. Read Data & Write Data4. TRIM to the rescue5. Patriot Torqx M28 256MB6. Test System7. ATTO Disk Benchmark8. Crystal DiskMark9. HD Tune10. HD Tach11. PCMark Vantage HDD Test12. Copying Test13. Game Level Load Test14. Video Combining Test15. Conclusion16. View All»