Fast-paced are SSDs – when they slip fresh from the packaging. Manufacturers like to brag about performance with powerful impressions. Of 500 MB / s and more is the talk. But as so often, the truth looks a little different. After all, the performance loss of an SSD can be measured even after the first application of the operating system.
So you have to reckon
We looked at this aspect of the popular flash memory in the test lab. In addition, we were interested in how it is about the longevity of the now quite cheap super storage. The result of our exemplary "SSD Kill Test" confirms the fact that the storage devices lose their performance with increasing usage. Above all, the quality of the memory used seems to have an influence on the strength of this power drop.
Why the power break?
For our stress tests, we use the Iometer tool, which allows various writing and reading scenarios. We always describe the SSD completely. Our normal stress test runs over several days, depending on the size and speed of the SSD. The state in which the volume is located after this stress test should be roughly comparable to a Windows operating system, which has already been loaded with various programs and has been in operation for several months.
Creeping Death
Particularly noticeable is the power break at the mean read access time. The Samsung 830 needs more than twice as much time as the ADATA SX910. The Plextor M5 Pro also takes about 50 percent more time - but with an access time of 0.091 milliseconds is still ten times faster than the ADATA- Model. After all, there is hardly any significant difference in write access.
Guide: Optimal Windows 7 settings for SSDs
Unfortunately, it is just the read accesses, which are particularly responsible for the intoxicating speed feeling of the SSDs. If an SSD can transfer data to the main memory at tremendous speed, it is impressive, but if the SSD needs a "half eternity" to find the file, then the high transfer rate only uses something when it is big Files. IOPS (Input-Output Operations per Second) for 512 KB files is particularly strong.
In this query, e.g. The Samsung over 50 percent of their power. With 5396 IOPS it is still second in this test field. The ability to achieve many IOPS in both large, medium, and small files is important for SSDs serving as system memory for the operating system. From this point of view, the Plextor M5 Pro and the Samsung 830 are highly recommended because, despite the expected performance drop, a very good overall performance of the IOPS is still maintained.
The main reason for the power loss is the logical structure of an SSD. For SSDs, data such as HDDs can not be easily overwritten. The erasure process requires the formation of blocks. The more data on an SSD, the more "pre-work" the controller must be able to afford to store new data.
Buying advice: Market overview SSD drives
The work is made particularly difficult by the fact that the description of the memory cells is distributed uniformly in order to avoid early "aging" of individual cells. This is called "wear levelling". If one did not pay attention to this distribution, individual memory cells could no longer be described in a very short time.
At some point, however, the memory of each cell is precipitated. Some vendors state that their MLC SSDs allow 10,000 write accesses. Others say that each individual cell can be described about 300 times. Basically, both of them mean the same thing, because with a writing process is meant only the description with a file of unspecified size. The fact that write operations are limited is due to the physical structure of the cell, which allows only a limited number of deletions.
How to set up SSDs best
At each erasure the cells are completely flooded with electrons. The "tunnel oxides", a material that is responsible for the load retention, are used. After about 300 deletions, the supply of tunnel oxide in the cell is exhausted with the MLC technology. High-quality, but also expensive SLC memory modules hold about ten times longer than their pre-rated MLC colleagues.
Death to the SSD
For most SSDs, it is possible to read the so-called SMART data. This works with vendor or external tools such as HD Tune. However, these are different from controller to controller. An indication is particularly important: "SSD Life Left" indicates the remaining lifetime. At 10 percent, all reserve blocks are used up and the exchange is urgently required.
At 0%, reading the data is still possible at best. The "Drive Life Protection Status" indicates whether the SSD rejects deletion operations that want to perform "wear levelling". The value is then "only" 90 instead of 100, but that too is already very bad!
Download: Table
No comments:
Post a Comment