Monday, August 13, 2012

The Benchmark of SSD and HDD, 5 things you should have already known about SSD

Well, a SSD, which stands for Solid State Drive, it's used for data storage, just like a Hard Disk Drive (HDD). We have compile a few section that can help our readers to know more about SSD, and we also have done some testing to the performance of SSD and HDD, check them out at the last section.

First of all, how do they look like?



In the stores you probably would see them packaged nicely and sold just like these.




On the insides:

This is how a Solid State Drive look like without a chassis.



This is a Hard Disk Drive, without it's cover.



Few things you should know already about SSD


In various ways, the SSD differs alot from HDD, because of their architecture, they were used for different purpose in the past. However as the price of SSD is reducing, it is reasonable for the market to purchase it now.

1. The controller and flash chip
As you can see, the SSD's architecture component made of a controller and flash chips. The flash chip has been developed as a non-volatile memory since 2009, therefore it doesn't need electricity to retain the data stored in it. During the event of power outage, there is no data loss. Since there is no moving parts in SSD, the performance of SSD is measured by its Input/Output Operations Per Seceond (IOPS).

2. It can withstand shock
In the past it was used by the military and aerospace industries due to SSD's characteristic that is able to withstand shock, vibration and temperature ranges. Why didn't they use the HDD? Look inside them, there's a rotating disk, and there's a writing mechanism in it, especially the writing head, if someone bangs the wall of the computer casing, the writing mechanism will be affected, and there will be data lost/error due to that.

3. Able to withstand heat
As for temperature range, some of the servers that has hard disk drive in it needs ventilation or at least some cooling, as Seagate mentioned that the surrounding temperature above 35 degrees Celsius will affect the life of the hard disk and it's reliability will be weakened if the drive temperate is above 55 degrees Celsius. SSD generally can withstand higher temperature and they don't require and cooling or ventilation. Except for those higher end enterprise models in the server farm where the add-on will be supplied with a heat sink.

4. Won't be affected by magnetic field
Hard disk drive read and write mechanism can be affected magnetic field. Magnets or magnetic surges could damage data, although the magnetic platters are usually well-shielded inside the metal case. Since SSD doesn't have have any parts that requires magnetism, so it won't be affected by magnetic field.

5. The reliability and its lifespan
The SSD doesn't have any moving parts in it, therefore it won't fail mechanically. The flash disk can be only erased and written a limited number of time before it fails. The controller is used to manage this limitation, thus prolong its life span. However SSDs based on DRAM do not have a limited number of writes.


How they store data and how it will affects SSD life span?


Flash Memory
SSD is actually similar to their relatives, the USB drive, it store most of the data in the flash memory. RAM on the other hand stores data too, but when there's no electricity, or when the system reboots, the data in the RAM will be lost. 

There's 2 type of NAND ( Negated And or Not And) Flash: Single Layer Cell (SLC) and Multi Layer Cell (MLC). SLC is where a unit is able to store 1 bit, which can be represented as 1 and 0, and the life span of SLC is longer, which is around 100,000 time. Whereas MLC can store 2 bit, which can be represented as 00, 01, 10, 11, therefore the storage is much denser than SLC. Although the cost of MLC is lower but its life span is shorter, which is around 10,000 times of storing and extract. 

Besides, the reading speed of SLC is faster than MLC, even though SLC's performance is better than MLC, but it's cost is higher, and twice the price of MLC. However the current production of MLC is getting more advanced, most of it will soon have the same read write speed similar to the SLC. At the moment the market's mainstream products are based on MLC, therefore the price of SSD is getting cheaper. 

Controller
The controller is like the brain of SSD, it has 3 main function, error correction, bad block mapping and garbage collection.

Our Michaelsoft DDS servers is able to support the usage of SSD, to ensure the peak performance of the servers and prolong the life span of SSD. Our Michaelsoft DDS is able to support TRIM command, which helps the SSD to recycle the discarded data.

The way SSD stores data is different, the term garbage collection illustrate how the data is written, delete, and rewrite.


TRIM enables the SSD to handle garbage collection overhead, which would otherwise significantly slow down future write operations to the involved blocks, in advance. 

What happens if the server OS that uses SSD doesn't use TRIM? To erase the data and rewrite, some of the SSD will experience wear and tear (write amplification), remember that the flash drive's life span? The MLC can only store 2 bits for only 10,000 times! 

SSD that experience write amplification will have reduced life span.

Therefore Michaelsoft DDS server OS has TRIM command that can ensure the performance of SSD due to garbage collection.


Experiment Section:

We have our own in house technicians to do the testing of the SSD and HDD, and the following are the result of

1. 7200 rpm Hard Disk VS SSD:



2. In house benchmarking using ATTO Disk Benchmark


michaelsoft-in-house-testing-ssd-hdd-atto-benchmark


"As you can see, for traditional hard disk, the performance for hard disk in Gb/s and Gb/s controller doesn't  have any significant differences. The bottleneck is on the hard drive mechenical parts that cannot keep up with Gb/s controller bandwidth. Only SSD can overcome the bottleneck that traditional hard drive has. But the cache capacity in caviar black and RE4 has advantage over mid range hard drive, as having multiple request for same data from hard drive will slightly improve data transfer speed latency as well as pro long hard drive life span." - Michaelsoft's Technician.



In conclusion, SSD's speed is faster than HDD, it can perform better, but with a higher cost. However, for Michaelsoft DDS, using SSD for the server is better as it will boot applications faster than using HDD. Contact US Michaelsoft DDS to check for whether if your server is suitable to use SSD for our Michaelsoft DDS diskless solution.





  • Check our previous blog entry where our client's 300 PCs cybercafe using our Michaelsoft DDS, where they use Kingston's Hyper X SSD.
  • This is our current month promotion, where you can get FREE Auto Game Update and Battle LAN. Terms and conditions applied.








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