Robert Milkowski wrote:
Hello John,
Thursday, November 9, 2006, 12:03:58 PM, you wrote:
JC> Hi all,
JC> When testing our programs, I got a problem. On UFS, we get the number of
JC> free inode via 'df -e', then do some things based this value, such as
JC> create an empty file, the value will decrease by 1. But on ZFS, it does
JC> not work. I still can get a number via 'df -e', and create a same empty
JC> file, the value is not my expectation. So I use a loop to produce empty
JC> files and watch the output of 'df -e'. After some long time, the number
JC> is 671, then 639, 641, 603, 605, 609, 397, 607...
JC> I check the number of files, yes, it increases steadily.
JC> Could you explain it?
UFS has static number of inodes in a given file system so it's easy to
say how much free inodes are left.
ZFS creates inodes on demand so you can't say how much inodes you can
create - however I guess one could calculate maximum possible number
of inodes to be created given free space in a pool/fs.
Yup, this is what ZFS does. It makes a *very rough* estimate of how
many empty files could be created given the amount of available space.
This number may be useful as some sort of upper bound, but no more than
that.
-Mark
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