Thanks a lot for a detailed explanation - now everything fits into places :) Some answers: 1) Filesystem in use is ext4 at all cases 2) Im not using discard option as Im not very aware how to use it - is it a filesystem mount option for fstab? 3) OS is CentOS 6.3 with RHEL OpenVZ patched kernel (2.6.32-042stab061.2 #1 SMP Fri Aug 24 09:07:21 MSK 2012 x86_64 x86_64 x86_64 GNU/Linux) Kind regards, -- ---------------------------------------------- Andres Toomsalu On 02.11.2012, at 12:37, Zdenek Kabelac wrote: > Dne 31.10.2012 01:04, Andres Toomsalu napsal(a): >> Hi, >> >> I'm a bit puzzled with some thin LV usage stats - hope that someone can shed a light on this. >> lvs shows that thin_backup LV is 94% used - but df shows only 16% - where comes the difference? >> >> lvs -a -o+metadata_percent >> LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Meta% >> pool VolGroupL0 twi-a-tz 1,95t 35,17 2,79 >> [pool_tdata] VolGroupL0 Twi-aot- 1,95t >> [pool_tmeta] VolGroupL0 ewi-aot- 14,00g >> root VolGroupL0 -wi-ao-- 10,00g >> swap VolGroupL0 -wi-ao-- 16,00g >> thin_backup VolGroupL0 Vwi-aotz 600,00g pool 94,51 >> thin_storage VolGroupL0 Vwi-aotz 600,00g pool 20,98 >> >> >> df -h >> Filesystem Size Used Avail Use% Mounted on >> /dev/mapper/VolGroupL0-root >> 9,9G 1,3G 8,1G 14% / >> tmpfs 16G 0 16G 0% /dev/shm >> /dev/sda1 1008M 122M 835M 13% /boot >> /dev/mapper/VolGroupL0-thin_storage >> 591G 39G 523G 7% /storage >> /dev/mapper/VolGroupL0-thin_backup >> 591G 90G 472G 16% /backup >> >> Thanks in advance, >> > > > As Stuart posted values are not related closely together. > But there are few things which are visible: > > ~35% tells you the number of used space in the pool - around ~700GB > ~3% metadata takes - ~400MB > > thin_backup has provisioned ~95% -> ~570GB > thin_storage ~21% -> ~130GB > > which seem to match approximately number of used blocks from the pool > (~570 + ~130 = ~700) > > === > > Now to interpret your 'df' stats: > > thin_storage uses 39GB stored in provisioned 130GB > thin_backup uses 90GB stored in provisioned 570GB > > and there could be multi reasons for this: > > - usage of large chunksize - and filesystem spreads a lot of data though the device - either for it's internal maintenance, or a lot of files are located > across whole provisioned space. > - You have delete lots of files - and have not used discard for deleted areas > (i.e. for ext4 there is 'fstrim' command which will discard them) > > > So here you need to provide more information which filesystem is in use, > and what was the overall usage for your devices. And also are you using discard support or not ? > What is the kernel version in use? > (It's always worth to use latest version of lvm2 - since there was improved > discard support configurability. > > Zdenek > > > > _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
