directory defrag

directory defrag

[Russell Coker]

The current defragmentation options seem to only support defragmenting named 
files/directories or a recursive defragmentation of files and directories.

I'd like to recursively defragment directories.  One of my systems has a large 
number of large files, the files are write-once and read performance is good 
enough.  However performance of "ls -al" is often very poor, presumably due to 
metadata fragmentation.

The other thing I'd still like is the ability to force all metadata allocation 
to be from specified disks.  I'd like to have a pair of SSDs for RAID-1 storage 
of metadata and a set of hard drives for RAID-1 storage of data.

-- 
My Main Blog         http://etbe.coker.com.au/
My Documents Blog    http://doc.coker.com.au/

Re: directory defrag

[Sander]

Russell Coker wrote (ao):
> The current defragmentation options seem to only support defragmenting
> named files/directories or a recursive defragmentation of files and
> directories.
> 
> I'd like to recursively defragment directories.

find / -xdev -type d -execdir btrfs filesystem defrag -c {} +

Would that work for you?

	Sander

Re: directory defrag

[David Sterba]

On Tue, Apr 14, 2015 at 07:37:17AM +0000, Russell Coker wrote:
> The current defragmentation options seem to only support defragmenting named 
> files/directories or a recursive defragmentation of files and directories.
> 
> I'd like to recursively defragment directories.  One of my systems has a large 
> number of large files, the files are write-once and read performance is good 
> enough.  However performance of "ls -al" is often very poor, presumably due to 
> metadata fragmentation.

Ie. the directory metadata in the b-tree. That's possible, but not all
of the code is there. So fare only whole-tree defragmentation is
implemented, ie. the extent tree or any subvolume tree. We'd have to
extend the defrag api to take a key range and then use it to span the
directory key range.