Re: BTRFS, getting darn slower everyday

Am Sonntag, 7. Oktober 2012 schrieb Swâmi Petaramesh:

Le 07/10/2012 15:00, Martin Steigerwald a écrit :

quoted

I forgot to mention mount options? Which one do you use?

root@tethys:/etc# grep btrfs fstab
/dev/VG1/BTR_POOL    /    btrfs   
subvol=UBUNTU/@,space_cache,autodefrag,compress=lzo,relatime        0 0
/dev/sda2        /boot    btrfs   
subvol=UBUNTU/@boot,space_cache,autodefrag,relatime            0 0
/dev/VG1/BTR_POOL    /tmp    btrfs   
subvol=UBUNTU/@tmp,space_cache,autodefrag,compress=lzo,relatime        
0 0 /dev/VG1/BTR_POOL    /home    btrfs
subvol=UBUNTU/@home,space_cache,autodefrag,compress=lzo,relatime    0 0
/dev/VG1/BTR_POOL    /storage    btrfs   
subvol=STORAGE,space_cache,autodefrag,compress=lzo,relatime    0 0
/dev/VG1/BTR_POOL    /data/BIG        btrfs   
subvol=DATA/BIG,space_cache,compress=lzo,noatime    0 0
/dev/VG1/BTR_POOL    /data/VBOX_HIDDEN    btrfs   
subvol=DATA/VBOX_HIDDEN,space_cache,compress=lzo,noatime    0 0
/dev/VG1/BTR_POOL    /data/VBOX_VMS        btrfs   
subvol=DATA/VBOX_VMS,space_cache,compress=lzo,noatime    0 0

Hmmm, is the slowness on all of these?

For the VBOX volumes I would have a possible explaination for slowness.

Unless the subvolume is mounted with nodatacow, which it isn´t according 
to above output, every write to the VM image goes to a new location. Thus 
this increases fragmentation. While autodefrag might mitigate some of 
these, it may not be enough. AFAIK its only efficient for certain use cases. 
So or so it does not appear tha tthe VBOX volumes use autodefrag.

Could you try filefrag -v on some of the bigger VM image files?

I also wonder about the absence of inode_cache, but this could either be 
default by now or BTRFS remembers whether what has initially been set. But 
you could try this one. Especially on the filesystems with lots of inodes.

Thanks,
-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
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