Thank you. * I use RAW images because of it's easier to offline mount/chroot when some issue happens. * I call directly qemu instead of libvirt
I'll try to parse these parameters to a qemu-system call. El 8/4/19 a les 22:03, Friedrich Oslage ha escrit: > Yes. > > You'll have to use the virtio-scsi driver, to my knowledge it's the only > driver that supports block discards. > > Quick example: > > # create a new empty disk > $ qemu-img create -f qcow2 disk.qcow2 10G > > # check size, should only be a few kilobytes > $ du -sh disk.qcow2 > > # add it to your vm > $ virtsh edit your-vm > <disk type='block' device='disk'> > <driver name='qemu' type='qcow2' discard='unmap' > detect_zeroes='unmap'/> > <source dev='/tmp/disk.qcow2'/> > <target dev='sda' bus='scsi'/> > <address type='drive' controller='0' bus='0' target='0' unit='0'/> > </disk> > <controller type='scsi' index='0' model='virtio-scsi'> > <driver queues='4'/> > </controller> > > # in your vm, format and mount it > $ mkfs.ext4 /dev/sda > $ mount /dev/sda /mnt/discardtest > > # put some data on it > $ dd if=/dev/urandom of=/mnt/discardtest/dummy.bin bs=1M count=1000 > $ sync > > # on host, check size...it should be about 1GB > $ du -sh disk.qcow2 > > # in vm, delete file and trim it > $ rm /mnt/discardtest/dummy.bin > $ sync > $ fstrim /mnt/discardtest > > # on host, check size...should only be a few megabytes > $ du -sh disk.qcow2 > > > It works with other guest OSes as well, for Windows you just use the > Optimize-Volume cmdlets instead of fstrim. > > You also don't have to use qcow2 for backing. Anything that can handle > discards will do, including sparse files. > > > My advice, however, would be to use qcow2, since sparse files don't work > particularly well. Executing the example above would leave you with > about 300MB at the end instead of less than 10MB. > > Regards > Friedrich > > On 4/5/19 4:04 PM, Narcis Garcia wrote: >> No; I want to study the possibility of recovering allocated blocs of >> host filesystem when guest filesystem removes its files (unallocates its >> blocks). >> Host -> HD or SSD (independent) with sparse-mode image >> Guest -> Virtual SSD (to signal discards) >> >> >> El 5/4/19 a les 16:01, Pascal ha escrit: >>> hello, >>> >>> if I understand correctly, you want to study the possibility of >>> recovering deleted files from an SSD disk: is that right ? >>> >>> regards, lacsaP. >>> >>> Le jeu. 4 avr. 2019 à 08:24, Narcis Garcia <[email protected] >>> <mailto:[email protected]>> a écrit : >>> >>> Is there a way to specify a disk to be detected as an SSD drive? >>> >>> Once reached this, I want to look for the possibility to recover >>> host >>> space when a guest discards disk image blocks, and this image is >>> RAW >>> format and sparse allocated file. >>> >>> Thank you. >>> >
