Re: [libvirt-users] libvirt and lvm thin pool

On 08/02/2014 04:24 PM, Vasiliy Tolstov wrote: > Hi all. I'm using libvirt 1.2.6 > I want to use lvm storage for my virtual machines. > But i want to use new lvm2 feature - thin pool. How can i do that in > libvirt? If libvirt can't create it via pool xml, does (and how) to > use this setup under libvirt? > The 'Thin Pool' is avoided by libvirt, but volumes found a "Sparse" or "Snapshot" that are part of an lvm thin pool can be utilized by libvirt - although as the storage administrator understand that if the volume becomes "filled" - it will go "Inactive" The key to whether an lvm volume is found is the attributes as seen from the 'lvs' utility which spits out the following for example: # lvs LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert home fedora -wi-ao---- 136.72g root fedora -wi-ao---- 50.00g swap fedora -wi-ao---- 7.64g lv_test lv_pool swi-a-s--- 4.00m [lv_test_vorigin] 50.39 or for a filled and now inactive volume: # lvs LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert home fedora -wi-ao---- 136.72g root fedora -wi-ao---- 50.00g swap fedora -wi-ao---- 7.64g lv_test lv_pool swi-I-s--- 4.00m [lv_test_vorigin] 100.00 The 'Attr' column must have an active volume as seen by the 'a' in the 5th field and as Jan points out cannot be a "thin" pool as seen when there's a 't' in the first column. Assuming you know have the physical volume already created (via pvcreate), then a pool definition could be: # more lv_pool.xml <pool type="logical"> <name>lv_pool</name> <source> <device path="/dev/sdb2"/> <device path="/dev/sdb3"/> </source> <target> <path>/dev/lv_pool</path> </target> </pool> # Where the device path entries would be your physical volumes. Using 'virsh pool-build lv_pool' and 'virsh pool-start lv_pool' will set things up allowing for the creation of a volume in the pool such as: # more lv_test.xml <volume> <name>lv_test</name> <key>r4xkCv-MQhr-WKIT-R66x-Epn2-e8hG-1Z5gY0</key> <source> <device path='/dev/sdb3'> </device> </source> <capacity>8388608</capacity> <allocation>4194304</allocation> <target> <path>/dev/lv_pool/lv_test</path> <permissions> <mode>0660</mode> <owner>0</owner> <group>6</group> <label>system_u:object_r:fixed_disk_device_t:s0</label> </permissions> </target> </volume> via 'virsh vol-create lv_pool lv_test.xml' where the 'capacity' and 'allocation' values are the key to determining whether a 'sparse' or 'snapshot' volume from an lvm thin pool will be created. If capacity is not equal allocation, then the resulting libvirt command adds the '--virtualsize' (or '--V') to the lvm command used to create the volume in the pool, e.g. # /usr/sbin/lvcreate --name lv_test -L 4096K --virtualsize 8192K lv_pool John