Discards appear like they are being sent to the device. How big of a
temporary file did you create and then delete? Did you sync the file
to disk before deleting it? What version of qemu-kvm are you running?
On Tue, Mar 13, 2018 at 11:09 AM, Fulvio Galeazzi
<fulvio.galeazzi@xxxxxxx> wrote:
> Hallo Jason,
> thanks for your feedback!
>
> -------- Original Message -------->> * decorated a CentOS image with
> hw_scsi_model=virtio--scsi,hw_disk_bus=scsi> > Is that just a typo for
> "hw_scsi_model"?
> Yes, it was a typo when I wrote my message. The image has virtio-scsi as it
> should.
>
>>> I see that commands:
>>> rbd --cluster cephpa1 diff cinder-ceph/${theVol} | awk '{ SUM += $2 } END
>>> {
>>> print SUM/1024/1024 " MB" }' ; rados --cluster cephpa1 -p cinder-ceph ls
>>> |
>>> grep rbd_data.{whatever} | wc -l
>>
>>
>> That's pretty old-school -- you can just use 'rbd du" now to calculate
>> the disk usage.
>
>
> Good to know, thanks!
>
>>> show the size increases but does not decrease when I execute delete the
>>> temporary file and execute
>>> sudo fstrim -v /
>>
>>
>> Have you verified that your VM is indeed using virtio-scsi? Does
>> blktrace show SCSI UNMAP operations being issued to the block device
>> when you execute "fstrim"?
>
>
> Thanks for the tip, I think I need some more help, please.
>
> Disk on my VM is indeed /dev/sda rather than /dev/vda. The XML shows:
> .....
> <disk type='network' device='disk'>
> <driver name='qemu' type='raw' cache='none'/>
> .....
> <source protocol='rbd'
> name='cinder-ceph/volume-80838a69-e544-47eb-b981-a4786be89736'>
> .....
> <target dev='vda' bus='scsi'/>
> <serial>80838a69-e544-47eb-b981-a4786be89736</serial>
> <address type='drive' controller='0' bus='0' target='0' unit='0'/>
> </disk>
> <controller type='scsi' index='0' model='virtio-scsi'>
> <address type='pci' domain='0x0000' bus='0x00' slot='0x04'
> function='0x0'/>
> </controller>
>
>
> As for blktrace, blkparse shows me tons of lines, please find below the
> first ones and one of the many group of lines which I see:
>
> 8,0 0 11 4.333917112 24677 Q FWFSM 8406583 + 4 [fstrim]
> 8,0 0 12 4.333919649 24677 G FWFSM 8406583 + 4 [fstrim]
> 8,0 0 13 4.333920695 24677 P N [fstrim]
> 8,0 0 14 4.333922965 24677 I FWFSM 8406583 + 4 [fstrim]
> 8,0 0 15 4.333924575 24677 U N [fstrim] 1
> 8,0 0 20 4.340140041 24677 Q D 986016 + 2097152 [fstrim]
> 8,0 0 21 4.340144908 24677 G D 986016 + 2097152 [fstrim]
> 8,0 0 22 4.340145561 24677 P N [fstrim]
> 8,0 0 24 4.340147495 24677 Q D 3083168 + 1112672 [fstrim]
> 8,0 0 25 4.340149772 24677 G D 3083168 + 1112672 [fstrim]
> .....
> 8,0 0 50 4.340556955 24677 Q D 665880 + 20008 [fstrim]
> 8,0 0 51 4.340558481 24677 G D 665880 + 20008 [fstrim]
> 8,0 0 52 4.340558728 24677 P N [fstrim]
> 8,0 0 53 4.340559725 24677 I D 665880 + 20008 [fstrim]
> 8,0 0 54 4.340560292 24677 U N [fstrim] 1
> 8,0 0 55 4.340560801 24677 D D 665880 + 20008 [fstrim]
> .....
>
> Apologies for my ignorance, is the above enough to understand whether SCSI
> UNMAP operations are being issued?
>
> Thanks a lot!
>
> Fulvio
>
--
Jason
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