Disadvantages of solid state media (was Re: Advantages...)

Jochen Kunz wrote: It's certainly true that you can buy NAND flash chips with 512-byte pages; that is called "small-block NAND". They're commonly used in embedded systems. However, the high-density (e.g., 64 to 256 Gbit) NAND flash devices used in memory cards are normally "large-block NAND", with typical page sizes of 4K or 8K, and erase block sizes of 512KB or larger (1024 sectors or more!), so they do in fact have the blocking/deblocking problem I described. With regard to the this problem, the erase block size is general the bigger problem, since erase can only be done at the block level, not the page level. I can't give specific details from datasheets due to having to agree to NDAs to get the datasheets (ugh!), but look at the datasheets from most any of the major NAND flash vendors for their large-block NAND parts. The reason for the use of large-block NAND is that it is significantly less expensive than small-block NAND. Except at the high end of the flash-drive/flash-card market, cost is the overriding concern. As a result, far more R&D goes into large-block rather than small-block. Eric