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Intel Smart Response Technology

We decided to save the most interesting feature of the new Intel Z68 for last. The new chipset didn’t impress us with its overclocking potential, and Virtu technology seems to make sense only for those gamers who often transcode video. Therefore, Intel added another feature to their new Z68, which may become the major argument in favor of the new core logic set. This technology is called Intel Smart Response or simply SSD-caching, which is the name used previously.

Flash-based storage devices continue to expand their market presence with great success. SSD-drives have one indisputable trump – high speed. Therefore, SSDs are very welcome guests in any computer system: any user will immediately feel that with SSD applications load faster and files open quicker. However, SSDs are still pretty expensive, which is preventing a lot of users from replacing their conventional HDDs with the solid-state drives.

No wonder that in this situation many users choose the “transitional solution”, when there is a small and fast SSD functioning as a system drive and a slow large-capacity HDD used to store all the data. Having analyzed the situation, Intel decided to come up with a solution for these rationalists. Intel Smart Response technology implemented in Intel Z68 should create even more optimal conditions for small and fast system SSDs. Intel suggested turning them into a high-speed cache for the slow disk sub-system of conventional HDDs. In other words, Intel Smart Response allows combining SSDs with traditional hard drives within the same storage sub-system and enjoying maximum advantages of this symbiosis by automatically duplicating the most frequently requested data in a fast SSD. As a result, you will be able to access the most popular data stored in the SSD cache very quickly, which should dramatically improve the overall system responsiveness.

In fact, just like Lucid Virtu, Intel Smart Response is a software technology. It is implemented in the new Intel RST driver version 10.5. However, Intel has strictly tied up their Smart Response technology to the chipset: it won’t work on those LGA1155 mainboards that aren’t based on the Z68 core logic set. But at the same time Intel Smart Response will be supported in some mobile platforms on Intel HM67 or QM67 chipsets.

Intel Smart Response works in a very simple manner. The SSD is set as a caching storage device in the Intel RST driver interface. Right after that the operating system starts using it as a cache and sees the SSD + HDD combination as a single storage volume.

You can use SSDs with up to 64 GB storage capacity to serve as caching devices. Moreover, when Intel Smart Response is activated for larger capacity SSDs, it is possible to assign only part of the SSD drive for the needs of this technology.

Intel Smart Response technology has another limitation. You can only assign one caching SSD drive for one HDD or one disk array. In other words, if there are two hard disk drives in the system that aren’t within the same RAID array, you will need to get two SSDs to cache them both, or to split the capacity of your SSD in two halves to create two independent caches.

The algorithm behind Intel Smart Response technology is fairly simple. During the initial request for data on the hard drive (read or write), this data is simultaneously duplicated onto the caching SSD. In case of another request for the same data, it will be delivered not from the slow HDD, but from the fast cache, which speeds up the disk sub-system. When the SSD is filled with data completely, but a new position needs to be cached, then the system will remove the least frequently accessed data from it to free up some space. And due to the fact that SSDs use power-independent flash-memory, the cache contents are saved after all reboots and power-downs. This very easy to implement principle guarantees superb efficiency of Intel Smart Response technology.

However, Intel developers made Smart Response extra intellectual, which makes the use of SSD cache even more effective. Firstly, it is important that this technology is abstracted from the file system: it caches not the actual files but clusters. This makes the use of this cache more efficient. Secondly, Intel Smart Response can identify specific data access scenarios, which do not require transferring the data into the cache. For example, system virus scanning, HD video playback or simply copying large chunks of data from one drive to another.

Intel Smart Response technology offers two cache usage strategies. You can use Intel RST to switch between them at any time:

  • Enhanced. In this mode SSD cache works with write-through, which means that the results of all writes are immediately saved to the HDD. In this case the write speed of the Smart Response array is limited by the write speed of the HDD in it. But in any moment of time the integrity of the info on the hard drive is guaranteed 100%.
  • Maximized. In this mode we use an SSD cache with write-back. During writes only the data on SSD is modified, and then the changes are saved to the HDD later, during the idle time. As a result, the write speed in Smart Response array is significantly higher, but it may so happen that the HDD doesn’t have the latest file versions at certain point. Theoretically, it may cause data loss during emergency shut down or SSD failure.

Knowing how Intel Smart Response technology works, we should understand the importance of choosing the right SSD for the cache. A lot of inexpensive SSDs offer relatively low write speed and may even lose to contemporary HDDs in this aspect. In a Smart Response array the write speed is limited by the SSD writes even in Maximized mode, so in some cases Intel Smart Response technology may even slow down the disk subsystem altogether. The thing is that in Enhanced mode the write speed is determined by the writes of the slowest drive in the SSD-HDD combination, which can be either one. In Maximized mode the performance depends solely on the SSD.

Intel tried to resolve this issue by launching a special SSD developed directly for the use in Smart Response arrays. Please meet Intel Larson Creek or Intel SSD 311.

This 20 GB SSD is really great for the cache. Its major secret weapon is the use of 34 nm SLC NAND chips, which are more expensive than the popular MLC-flash, but boast tangibly faster writes and allow much greater number of rewrites. In other words, Intel SSD 311 has all the features that are important for the caching SSD drive.

Of course, it doesn’t break any performance records like OCZ Vertex 3 or Crucial M4 and supports only 3 Gbps SATA, but nevertheless, offers very good combination of features for its needs.

The only disappointment is the price: the 20 GB Intel SSD 311 costs around $100, i.e. about the same as the regular SSD drives with twice the capacity. This high price is the result of using expensive SLC-flash. However, it seems to be quite justified, because SLC NAND should ensure that Intel’s Larson Creek may continue functioning as cache for a much longer period of time than any drive with MLC-memory inside would.

 
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