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1. Comment - Samsung Builds Flash Based Disk Drive

   (May 25, 2005 - 6:06 PM)

   You have to understand that the internal memory controller of the hard drive takes into account wear leveling - we are not talking about raw flash memory cells, but about an integrated hard drive which uses flash memory.
   
   Wear Leveling extends the lifetime of NAND Flash devices because it ensures that even if an application writes to the same virtual blocks over and over again, the program/erase cycles will be distributed evenly over the NAND Flash memory.
   
   With wear leveling, you can achieve the stated lifetime of 50+ years. The MTBF calculation and lifetime statistic has to take into account the failure modes of the system as a whole, including the wear leveling technology that extends the lifetime of the flash memory cells.

2. Comment - Samsung Builds Flash Based Disk Drive

   (May 24, 2005 - 3:04 PM)

   I agree. The MTBF (Mean Time Between Failures) is a theoretical calculation derived from the reliability metrics of the individual components, their respective failure modes, at some target operating temperature.
   
   The max write cycles is an absolute limit usually based on the semiconductor properties within the memory device.
   
   I did not mean to imply that these two were one and the same.
   
   Please note that BitMicro stated a write frequency of 6,016,204,800 KB per day (68 MB/sec) - this is continuous usage of the device at a very high data rate. The endurance is much more than the lifetime of any computer system --> (in years) = 199,229 days / 365 = 72.59 years

3. Comment - Samsung Builds Flash Based Disk Drive

   (May 24, 2005 - 2:42 PM)

   MTBF specs vary based on the manufacturer and the calculation used; the following are some sample specs I have found:
   
   Pretec --> MTBF 500,000 hours (powered on)
   Simpletech --> MTBF 1M+ hours
   SanDisk --> MTBF 3M+ hours
   BitMicro --> MTBF 2M+ hours
   
   But the most reliable and experienced guys around are BitMicro, and this is what they pubish for one of their flash drives:
   
   http://www.bitmicro.com/...urces_flash_ssd_db2.php
   
   Example #2: Write Frequency in MB/sec
   
   E-Disk® PB Size = 16 KB
   
   I/O Block Size = 64 KB
   
   Write Frequency = 6,016,204,800 KB per day (68 MB/sec)
   
   E-Disk® capacity = 155,648 MB
   Number of Flash chips = 608
   Size of Flash chips = 2048 Mbit or 256 MB or 262,144 KB
   
   Number of writes to Flash chip = 64 KB / 16 KB = 4
   Total E-Disk® physical blocks = (262,114 / 16) x 608 = 9,961,472
   Total max writes to E-Disk® drive = 9,961,472 x 1,000,000 = 9,961,472,000,000
   
   Endurance (in days) = 9,961,472,000,000 / (4 X (6,016,204,800/64)) = 26,492 days
   Endurance (in years) = 199,229 days / 365 = 72.59 years
   
   It is interesting that SamSung has developed something very similar to what BitMicro has had for some time.