ZFS directory with a large number of files

Daniel Kalchev daniel at digsys.bg
Tue Aug 2 10:37:52 UTC 2011

On 02.08.11 12:46, Daniel O'Connor wrote:
> I am pretty sure UFS does not have this problem. i.e. once you 
> delete/move the files out of the directory its performance would be 
> good again. 

UFS would be the classic example of poor performance if you do this.

> If it is a limitation in ZFS it would be nice to know that, perhaps it 
> truly, really is a bug that can be avoided (or it's inherent in the 
> way ZFS handles such things)

It is possible  that there is not enough memory in ARC to cache that 
large directory.

Other than that, perhaps in ZFS it would be easier to prune the unused 
directory entries, than it is in UFS. It looks like this is not implemented.

Another reason might be some FreeBSD specific implementation issue for 

In any case, the data available is not sufficient. More information 
would help, like how much RAM this system has, how much ARC uses, some 
ARC stats.

What made me wonder is .. how exactly the kernel and zpool disagree on 
zpool version? What is the pool version in fact?


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