The limit isn't fixed, but varies depending on flash architecture, and is on average in the order of 1000 for the flash chip installed on Dockstars. There's a limit on the number of erase operations that can be performed on a block, as each such causes permanent deterioration that reduces the block's remaining usable life. When writing to a (previously erased) page, or reading from a page, other pages within the same block are exposed to voltages that can change the state of individual bits, leading to subsequent bit errors. NAND flashes are prone to developing bit errors, not only after repeated block erasures and write operations, but also after any read from a page on flash storage. (Note: I refuse to use the obscene notation KiB, MiB, etc, that some elements are trying to force feed on us.) Sector size is dependent on the software that does the ECC, but is typically 512B. On the Dockstar, blocks are 128KB, pages are 2KB user data plus 64B OOB. The ECC codes for each sector are grouped together and stored in the OOB area of each page. The user data in a page is also logically divided into smaller units called "sectors", which are the units of data over which individual ECC is generated or correction performed. It contains both the user data, and some out-of-band (OOB) data used for storing bad block markers, ECC (Error Correcting Code) and FTL (Flash Translation Layer) information. It is in essence a window into a location on flash. A page is the smallest amount of data that is read from or written to flash storage. Each block is further divided into "pages". A block is the smallest unit of storage that can be erased at a time. Data on NAND flashes are organized in blocks. The dockstar didn't even see the USB stick, so I might have wrote the image wrong.įor anyone contemplating using either of (Jeff) Doozan's bootloaders, any of the 2-stage bootloaders available, and/or a distribution like OpenWrt's current official JFFS2 based build, I think it's important to know the implications that no one is telling.Ī little bit of background is in order. It didn't work for me when I tried to run it. I've got the boot loader working, but was under the impression that the build here is some how borked.
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