Can I convert 33T logical partitions?

[h77626592]

The ext4 logical partition made of three hard disks, the data is about 20T, and the conversion to xfs is wrong. How to solve this problem?

10:04:13 dd: Unable to target output file”/tmp/fstransform.mount.120513/.fstransform.loop.120513 35994497712127 Truncate at byte: file is too large

[h77626592]

The logical partition size is 33T

[cosmos72]

Short answer: an ext4 33TB filesystem is currently too large for conversion with fstransform; the current limit on ext4 is 16 TB.

Long answer:
fstransform creates inside the filesystem to be converted a single sparse file as large as the filesystem itself, then formats the sparse file (to xfs, in this case), loop-mounts it and progressively moves data from the ext4 filesystem into the loop-mounted xfs sparse file.

Unluckily, ext4 maximum file size is 16 TB - see https://en.wikipedia.org/wiki/Ext4 - thus the error you reported.

A possible, future, solution could be to create several smaller files, and view them as a single block device using Linux Device Mapper instead of the current solution that uses loop devices. This would require modifying fstransform, clearly.