To amplify what Mike says... On Jul 10, 2012, at 5:54 AM, Mike Gerdts wrote: > ls(1) tells you how much data is in the file - that is, how many bytes > of data that an application will see if it reads the whole file. > du(1) tells you how many disk blocks are used. If you look at the > stat structure in stat(2), ls reports st_size, du reports st_blocks. > > Blocks full of zeros are special to zfs compression - it recognizes > them and stores no data. Thus, a file that contains only zeros will > only require enough space to hold the file metadata. > > $ zfs list -o compression ./ > COMPRESS > on > > $ dd if=/dev/zero of=1gig count=1024 bs=1024k > 1024+0 records in > 1024+0 records out > > $ ls -l 1gig > -rw-r--r-- 1 mgerdts staff 1073741824 Jul 10 07:52 1gig
"ls -ls" shows the length (as in -l) and size (as in -s, units="blocks") So you can see that it takes only space for metadata. 1 -rw-r--r-- 1 root root 1073741824 Nov 26 06:52 1gig size ................................ length -- richard -- ZFS Performance and Training richard.ell...@richardelling.com +1-760-896-4422
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