Apparatus and methods for fast and secure storage of data

1. A data storage method comprising the steps of:

providing a data storage apparatus with a cache memory module and a NAND flash memory module, wherein the cache memory module comprises a cache memory;

selecting a portion of the NAND flash memory module as a cache memory mirror;

selecting another portion of the NAND flash memory module as a user data storage zone;

transferring a write command that comprises user data into the cache memory module from a host;

writing a copy of the user data into the user data storage zone from the cache memory module in a write-back mode;

writing another copy of the user data into the cache memory mirror from the cache memory module in a write-through mode;

determining whether any of the user data are lost from the cache memory module before all of the user data are written into the user data storage zone comprising the steps of:

setting a write pointer for every page of the user data stored in the cache memory mirror;

setting a flush pointer for every page of the user data stored in the cache memory mirror;

determining whether the write pointer is larger than the flush pointer; and

updating the flush pointer every time the user data are written into the user data storage zone from the cache memory module; and

copying the user data stored in the cache memory mirror and writing the user data into the cache memory module which then writes the user data into the user data storage zone in the write-back mode when the data storage apparatus is rebooted if some of the user data are lost from the cache memory module before all the user data are written into the user data storage zone.

2. The data storage method according to claim 1 , wherein the step of copying the user data stored in the cache memory mirror and writing the user data into the cache memory module comprising the steps of:

writing a page that follows the page represented by a flush pointer to a last page into the cache memory module from the cache memory mirror; and

setting logical allocation addresses for the user data.

3. The data storage method according to claim 1 , wherein the step of transferring a write command that comprises user data into the cache memory module from a host comprises the steps of:

determining whether the host gives a write command;

transferring the user data into the cache memory module from host if the host gives a write command; and

stopping the process if the host does not give a write command.

4. The data storage method according to claim 1 , wherein the step of writing another copy of the user data into the cache memory mirror from the cache memory module in a write-through mode comprises the steps of:

determining whether the size of space for storage of data left in the memory mirror is smaller than that of the write command;

if the size of space for storage of data left in the memory mirror is smaller than that of the write command, executing the steps of:

flushing the user data into the user data storage zone from the cache memory; and

selecting another portion of the NAND flash memory module as the cache memory mirror.

5. The data storage method according to claim 1 , wherein the step of writing the user data into the cache memory mirror from the cache memory module further comprising the step of telling the host that the user data have been written into the cache memory mirror from the cache memory module.

6. The data storage method according to claim 1 , wherein the step of writing another copy of the user data into the user data storage zone from the cache memory module in the write-back mode comprises the steps of:

determining whether an amount of dirty data reaches a predetermined value; and

flushing the user data into the user data storage zone from the cache memory module and updating the flush pointer if the amount of the dirty data reaches the predetermined value.