Can I change the zfs record size of an existing share or LUN?
The record size can be changed for a share, but not a LUN. Changing the zfs record size will only affect future writes. It will not change any of the data already written to the share. Anything that causes the file to be rewritten will cause the new record size to be used. For example, if you open a file and save it, the new copy will reflect the new block size.
