Is there a maximum size for a BFS volume?


#1

Is there a maximum size for a BFS volume?

I searched and cannot find relevant information.


#2

2EB

Granted it probably has alot of other shortcomings before you hit that particular limit!

This book is about BFS… a good informative read. It’s also the official documentation of the FS, not sure it explicitly states 2EB, but if you read it and figure out the limitations the superblock, you should be able to figure it out exactly.
http://www.nobius.org/~dbg/practical-file-system-design.pdf


#3

The max file size of ~260GB is much more likely to be reached than the max volume size will be any time soon.

I do seem to remember the 260GB max file size is a current limitation. I thought the theoretical file limit was in the petabyte range.

Filling a terabyte drive with only four files? Sounds fun. :grin:


#4

Not obviously stated in the book but on p. 48, there is a reference to 2^58 bytes with a 1 KB block size.

However, going through the logic for the determination of the size of the allocation group, this size should be set such that the file limit is larger than the drive size (see pp. 105-106).

Also on p> 106, there is a note that with the “unused” triple-indirect block, the file limit can be raised to around 512 GB which would suggest this as the largest disk size.

So, rather confusing and the way the code for BFS and its supporting utilities was written may impose smaller size limits.


#5

Yeah, that book was written when 1GB drives were still the norm.

Note file limit != volume limit. So maybe that is still accurate.