Calculating the life of an SD card
Paul_Dlk
Posts: 19
Hi all,
can anybody confirm my calculations relating to the life of an Sd card? I am using the formula provided in the SanDisk white paper at
http://www.sandisk.com/Assets/File/OEM/WhitePapersAndBrochures/RS-MMC/WPaperWearLevelv1.0.pdf .
I have a 512 MB uSD card. There is approx 300MB of fixed read only files on the card. I also have a number (from 3 to 75 in groups of 3) of very small files (12 bytes each). A group of 3 files get updated in a 'rolling robin' sequence ( File 1 updates, then File 2 updates, then File 3 updates, then File1 updates....). A write occurs to one of these three files every 100mS. The card is formatted with a cluster size of 32K.
My calculations show that the card will last 1,268 years. Is this correct or am I using the formula incorrectly. Although the file size that I am updating is only 12 bytes, I have entered it as 1K in the formula.
Paul
can anybody confirm my calculations relating to the life of an Sd card? I am using the formula provided in the SanDisk white paper at
http://www.sandisk.com/Assets/File/OEM/WhitePapersAndBrochures/RS-MMC/WPaperWearLevelv1.0.pdf .
I have a 512 MB uSD card. There is approx 300MB of fixed read only files on the card. I also have a number (from 3 to 75 in groups of 3) of very small files (12 bytes each). A group of 3 files get updated in a 'rolling robin' sequence ( File 1 updates, then File 2 updates, then File 3 updates, then File1 updates....). A write occurs to one of these three files every 100mS. The card is formatted with a cluster size of 32K.
My calculations show that the card will last 1,268 years. Is this correct or am I using the formula incorrectly. Although the file size that I am updating is only 12 bytes, I have entered it as 1K in the formula.
Paul
Comments
• Flash Cell Endurance: For Multi-Level Cell (MLC) Flash, up to 10,000 write cycles
per physical sector. For Single-Level Cell (SLC) Flash, up to 100,000 write cycles per
physical sector.
According to Toshiba, the inventor of·Flash Memory·“the 10,000 cycles of MLC NAND is more than sufficient for a wide range of consumer applications, from storing documents to digital photos. For example, if a 256-MB MLC NAND Flash-based card can typically store 250 pictures from a 4-megapixel camera (a conservative estimate), its 10,000 write/erase cycles, combined with wear-leveling algorithms in the controller, will enable the user to store and/or view approximately 2.5 million pictures within the expected useful life of
the card.”1
For USB Flash drives, Toshiba calculated that a 10,000 write cycle endurance would enable customers to “completely write and erase the entire contents once per day for 27 years, well beyond the life of the hardware.”
http://www.kingston.com/products/pdf_files/FlashMemGuide.pdf
·
For example, Kingston’s CompactFlash cards have a rated error specification of less
than one (1) bit in 1,000,000,000,000,000 bits read (1 bit per 1015 bits read).
·
http://www.storagesearch.com/ssdmyths-endurance.html
·
http://www.ocztechnologyforum.com/forum/forum.php
I use a 16G SLC CF card in my toughbook With Linux .. [noparse]:)[/noparse]
Peter KG6LSE
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