When converting 'Entire Disk', Osmosis will actually convert the content one partition at a time. Each partition must then be loaded into RAM in order for the conversion to proceed. By simply allocating enough RAM to the Osmosis Application to open the largest partition, the low memory message can be avoided.
First close out of all programs and open the Osmosis Folder. Single click on the Osmosis application to highlight it. 'Get Info' by holding down the Command Key and the letter I Key. Next, a dialog box comes up called Osmosis Info. Then click on the General Information pull down menu and select Memory. Preferred size should be increased to at least 50,000 kbytes, or 50 MB. If the computer has more RAM available, increasing the RAM size even further can often help.
If there is not enough memory available on the computer, then converting multiple samples in a partition instead of the entire disk can be a viable option.