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).

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.

Pathname length

PATH_MAX (1024) bytes, not including the mountpoint or the terminating NUL.

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.

Maximum number of files

The same as the maximum number of inodes.

This number can be set by either mkqnx6fs (with the -i option), or mkqnx6fsimg (with the num_inodes attribute in the buildfile). Both utilities assign default values if the number isn't specified.

You can query this value at any time with df -g mountpoint, where the variable is set to the Power-Safe filesystem mountpoint. The chkqnx6fs -S option also shows this value.