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choosing_sd_card [2018/07/10 10:40] akuzmukchoosing_sd_card [2022/01/14 23:47] (current) – ↷ Links adapted because of a move operation 127.0.0.1
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-====== SD cadrs comparison ======+====== How to select a proper SD card ====== 
 + 
 +WebHMI requires SD to work. On this page we will explain how to select a best card that will suit your needs. 
 + 
 +{{ network:insert-sd-card.jpg?direct&912 |}} 
 + 
 +===== SD cards comparison =====
  
 There is a wide variety of SD cards. In addition to the obvious differences, such as brand, formfactor and volume, Secure Digital memory cards also differ in the type of Flash-cells (SLC / MLC), class (4, 6, 8, 10) and overall performance. There is a wide variety of SD cards. In addition to the obvious differences, such as brand, formfactor and volume, Secure Digital memory cards also differ in the type of Flash-cells (SLC / MLC), class (4, 6, 8, 10) and overall performance.
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 Industrial SD cards provide a wider temperature range, uniform deterioration of cells due to wear-leveling, but have a higher price. Industrial SD cards provide a wider temperature range, uniform deterioration of cells due to wear-leveling, but have a higher price.
  
-So in each concrete case it is necessary to find the compromise between volume, reliability, price, availability. That's why WebHMI comes without a memory card. It is assumed that the card will be selected by the integrator based on the requirements that are imposed on the system.+So in each specific case it is necessary to find the compromise between volume, reliability, price, availability. That's why WebHMI comes without a memory card. It is assumed that the card will be selected by the integrator based on the requirements that are imposed on the system.
  
 //Please note that using a low-quality or fake memory card may result in **data loss** or unstable WebHMI operation. DO NOT use cards of doubtful origin. Preference is given to industrial memory cards. When you write a large amount of data, the lifetime of commercial cards in WebHMI can be only a few weeks after which the card goes down.// //Please note that using a low-quality or fake memory card may result in **data loss** or unstable WebHMI operation. DO NOT use cards of doubtful origin. Preference is given to industrial memory cards. When you write a large amount of data, the lifetime of commercial cards in WebHMI can be only a few weeks after which the card goes down.//
  
 +{{ network:sd-industrial.png?direct&912 |}}
 +On this photo: Industrial-grade card (left) works for years under heavy load and this commercial-grade card (right) died after 2 months of work. Both cards are from the same manufacturer.
 +
 +===== Benchmark =====
 We tested five different memory cards in order to understand their performance differences applicable to WebHMI. The test consists of writing 60,000 rows into a data table for graphs (5 columns). We tested five different memory cards in order to understand their performance differences applicable to WebHMI. The test consists of writing 60,000 rows into a data table for graphs (5 columns).
  
-The test involved such drives:+The test involved such disks:
  
   * Silicon Power 4GB Class 4 MLC   * Silicon Power 4GB Class 4 MLC
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 At the same time, the use of MLC-memory is advisable in systems with higher requirements for recording speed and/or the need to store a large amount of data. Or where the SLC memory does not fit into the budget of the system. At the same time, the use of MLC-memory is advisable in systems with higher requirements for recording speed and/or the need to store a large amount of data. Or where the SLC memory does not fit into the budget of the system.
 +
 +===== Test your card =====
 +How to find a faster card? Test all of your candidates!
 +
 +WebHMI has a built in benchmark to test performance of a particular card. Go to page **Maintenance->Disk Usage->SD card speed test** and press **Run test** button. Test runs up to 1 minute. After test will be completed you will see how many writes to database per second your card can handle.
 +
 +Here is example of such test run:
 +
 +{{ network:sd-card-speed-test.png?direct&912 |}}
 +
 +===== 2017 Update =====
 +After a few years of running various cards we have found that Transcend Industrial 1GB SLC cards suit our needs in most cases. So we can sell these cards with WebHMI by request.
 +
 +{{ network:cards.jpg?direct&912 |}}
 +
choosing_sd_card.1531219222.txt.gz · Last modified: 2018/07/10 10:40 by akuzmuk

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