Can be this rotational detection be affecting in this case? https://lists.openvz.org/pipermail/users/2019-April/007564.html (Devuan 1.0 VM with distro kernel succeeds with lsblk and fstrim)
How can I make guest OS to detect device as no rotational or true SSD? El 10/4/19 a les 12:47, Narcis Garcia ha escrit: > Pascal, I don't understand syntax you use for lsblk. > I see this with: > $ cat /sys/block/sda/queue/rotational > > > El 10/4/19 a les 12:38, Pascal ha escrit: >> it's ok with discard=unmap option (even if the disc is thick-provisioned) >> : the block used by the test file appears (VM side) or is reset (host >> side) at zero. >> >> notice that lsblk "thinks" that the disc is a rotational disk (eg. not >> really SSD) : >> >> lsblk -ndo /dev/sda >> 1 >> >> thanks for explanations ! >> >> Le mar. 9 avr. 2019 à 20:38, Narcis Garcia <informat...@actiu.net> a écrit : >> >>> I see now the simple: >>> -device virtio-scsi-pci >>> makes all -disk (media=disk) to be detected by guest as SSD >>> >>> Additionally, adding "discard=unmap,detect-zeroes=unmap" to disk image >>> specification makes host Qemu to discard sparse image holes and recover >>> host disk space when guest sends discard signal! >>> >>> This is my successful test with Debian 9 (stable): >>> >>> $ dd if=/dev/zero of=ssd.img obs=1M seek=128 count=0 >>> $ qemu-system-... -device virtio-scsi-pci -drive >>> file=ssd.img,media=disk,index=0,discard=unmap,detect-zeroes=unmap >>> >>> Thank you everyone. >>> >>> >>> El 9/4/19 a les 19:19, Friedrich Oslage ha escrit: >>>> 1. You need to set the discard option for the -drive parameter, eg >>>> -drive if=none,...,format=raw,discard=unmap since the default is still >>>> to simply ignore discards. >>>> >>>> You may also want to set the detect-zeroes option to unmap, to discard >>>> all-zero blocks instead of actually writing them. >>>> >>>> >>>> 2. The disk image you created is thick-provisioned. How is qemu supposed >>>> to discard anything in that file? It could turn it into a sparse file or >>>> overwrite it with zeroes I suppose, but both options are undesirable. >>>> >>>> To make use of the discard operation your backing storage has to support >>>> it. Either by beeing thin-provisioned, like qcow2 or raw sparse files, >>>> or by actually beeing a ssd/nvme disk. >>>> >>>> >>>> 3. Your testing method is flawed. You are using a journaling filesystem >>>> to write the data but to read it you access the block device directly . >>>> Even if the discard operation was working strings(1) would still show >>>> the hello-world string in the journal. >>>> >>>> You could try something like this: >>>> >>>> $ echo hello, world > /dev/sda >>>> $ strings /dev/sda >>>> $ blkdiscard /dev/sda >>>> $ strings /dev/sda >>>> >>>> >>>> Regards >>>> Friedrich >>>> >>>> On 4/9/19 4:38 PM, Pascal wrote: >>>>> the blocks do not seem to be discarded on a raw format disk: the data >>>>> remains on the disk... >>>>> >>>>> on host : >>>>> >>>>> dd if=/dev/zero of=/tmp/ssd.disk bs=1M count=128 >>>>> qemu -drive media=disk,file=linux.disk -device virtio-scsi-pci,id=scsi >>>>> -device scsi-hd,drive=hd -drive >>>>> if=none,id=hd,file=/tmp/ssd.disk,format=raw >>>>> >>>>> on Linux VM : >>>>> >>>>> fdisk /dev/sda >>>>> # create one partition on gpt type... >>>>> fdisk -l /dev/sda >>>>> Disk /dev/sda: 128 MiB, 134217728 bytes, 262144 sectors >>>>> Units: sectors of 1 * 512 = 512 bytes >>>>> Sector size (logical/physical): 512 bytes / 512 bytes >>>>> I/O size (minimum/optimal): 512 bytes / 512 bytes >>>>> Disklabel type: gpt >>>>> Disk identifier: B8D98B8E-7790-4043-8F37-D4D8CA218884 >>>>> Device Start End Sectors Size Type >>>>> /dev/sda1 2048 262110 260063 127M Linux filesystem >>>>> mkfs.ext4 -L ssd /dev/sda1 >>>>> mount /dev/sda1 /ssd >>>>> mount >>>>> /dev/sda1 on /ssd type ext4 (rw,relatime,data=ordered) >>>>> echo hello world > /ssd/test >>>>> cat /ssd/test >>>>> hello world >>>>> sync && sysctl -q vm.drop_caches=3 >>>>> rm -f /ssd/test >>>>> sync && sysctl -q vm.drop_caches=3 >>>>> fstrim /ssd >>>>> umount /ssd >>>>> strings /dev/sda1 | grep 'hello world' >>>>> hello world >>>>> >>>>> >>>>> Le mar. 9 avr. 2019 à 08:36, Narcis Garcia <informat...@actiu.net> a >>>>> écrit : >>>>> >>>>>> 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 <informat...@actiu.net >>>>>>>>> <mailto:informat...@actiu.net>> 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. >>>>>>>>> >>>>>> >>>> >>> >>> >
