Power-Safe (fs-qnx6.so) filesystem
The limits for Power-Safe filesystems (supported by fs-qnx6.so) include:
- Physical disk sector
- 32-bit (2 TB), using the devb API.
- Logical filesystem block
- 512, 1024, 2048, or 4096 (set when you initially format the filesystem).
- Maximum filename length
- 510 bytes (UTF-8). If the filename is less than 28 bytes long, it's stored in the directory entry; if it's longer, it's stored in an external file, and the directory entry points to the name.
- Maximum file size
- 64-bit addressing.
With a 1 KB (default) block size, you can fit 256 block pointers in a block, so a file that's 16 × 256 × 1 KB (4 MB) requires 1 level of indirect pointers. If the file is bigger, you need two levels (i.e. 16 blocks of 256 pointers to blocks holding another 256 pointers to blocks), which gives a maximum file size of 1 GB. For three levels of indirect pointers, the maximum file size is 256 GB.
If the block size is 2 KB, then each block holds up to 512 pointers, and everything scales accordingly.