On Jul 18, 2009 10:08 +1000, Neil Brown wrote: > It has recently come to by attention that Linux on a 32 bit host does > not handle devices beyond 16TB particularly well. > > In particular, any access that goes through the page cache for the > block device is limited to a pgoff_t number of pages. > As pgoff_t is "unsigned long" and hence 32bit, and as page size is > 4096, this comes to 16TB total. : : > I suppose we could add a CONFIG option to make pgoff_t be > "unsigned long long". Would the cost/benefit of that be acceptable? I think the point is that for those people who want to use > 16TB devices on 32-bit platforms (e.g. embedded/appliance systems) the choice is between "completely non-functional" and "uses a bit more memory per page", and the answer is pretty obvious. For users who don't want to support this, they don't have to (just like CONFIG_LBD or whatever), and for 64-bit systems it is irrelevant. I think years ago we had the idea that it would be 64-bit everywhere by now, and while that is true for many systems, embedded/appliance systems will probably continue to be 32-bit for as long as they can. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
