Xenserver does not reclaim space after deleting VDI or Snapshot.

The exact cause for the above error has already been mentioned in my older blog
To Solve this issue, do the following steps
Step 1: scan your SR for orphaned VHDs
vhd-util scan -f -m “VHD-*” -l “VG_XenStorage-<uuid_of_SR>” –p
for example:
[root@MytestCase]# vhd-util scan -f -m “VHD-*” -l “VG_XenStorage-99dfb8a9-2dcc-b610-45ca-2010fb0e475b” -p
vhd=VHD-75fa7730-091d-4d6b-bcae-79ae11efa79d capacity=21474836480 size=21525168128 hidden=1 parent=none
vhd=VHD-7ec19bd2-1c86-44c0-83f1-aab4c8bd7e41 capacity=26843545600 size=26902265856 hidden=1 parent=none
vhd=VHD-902f17f1-c254-4cde-8519-a004b8721581 capacity=64424509440 size=64558727168 hidden=1 parent=none
vhd=VHD-94bc9c71-6e33-4281-9c1d-9ecd6f1da4c0 capacity=16106127360 size=16143876096 hidden=1 parent=none
vhd=VHD-975c1983-449c-4021-9843-3a6f5d36f564 capacity=21474836480 size=21525168128 hidden=1 parent=none
vhd=VHD-cb0d1245-2445-455f-bb17-3331172def32 capacity=21474836480 size=21525168128 hidden=1 parent=none
vhd=VHD-d5c21ed0-3970-4ac9-8ce8-70a90f7ce147 capacity=16106127360 size=16143876096 hidden=1 parent=none
vhd=VHD-d6a48e7f-307c-4053-a2f2-f05e6abcab49 capacity=16106127360 size=16143876096 hidden=1 parent=none
vhd=VHD-fc646534-658a-4550-b7e8-f13c6fbfe935 capacity=16106127360 size=16143876096 hidden=1 parent=none
vhd=VHD-6a0e604d-439f-4ec5-85f1-090574cd8cce capacity=26843545600 size=26902265856 hidden=0 parent=none
Step 2: Make a full copy of the VM and delete the old VM. Then check whether the chain is removed from the SR. this process will remove the VHD chain whereas step 3 should be used to remove the Orphan VHDs
Step 3: if step 2 does not reclaim space, then try to remove the Orphan VHD
lvremove /dev/VG_Xenstorage-<uuid_of_SR>/VHD-uuid
For Ex:
[root@XENH3-TEST VG_XenStorage-3a490822-9d03-50ae-01a2-07e8d877bb17]# lvremove /dev/VG_XenStorage-3a490822-9d03-50ae-01a2-07e8d877bb17/VHD-b21c101c-8f66-4202-842a-eb7173bee109
  /dev/sdb: read failed after 0 of 4096 at 0: Input/output error
  /dev/sde: read failed after 0 of 4096 at 0: Input/output error
  Logical volume “VHD-b21c101c-8f66-4202-842a-eb7173bee109″ successfully removed
The above happens only if the VHD do not have a Symbolic link to it. you can check this by the following command
/dev/ VG_XenStorage-<uuid of ur SR># ls -l
Step 4: Change the hidden VHD to unhidden
vhd-util set -f hidden -v 0 -n <path to vhd file>
Note: to find out the path, type ls –l in /dev/ VG_XenStorage-<uuid of ur SR>
For Ex:
vhd-util set -f hidden -v 0 -n  /dev/mapper/VG_XenStorage–99dfb8a9–2dcc–b610–45ca–2010fb0e475b-VHD–6a0e604d–439f–4ec5–85f1–090574cd8cce
Now you will be able to see the VHD in the XenCenter.
Step 5: Now attach the disk to any VM, modify its size and start the VM
Now the disk which was used by dom 0 will be used by the VM
Step 6: Now stop the VM, then deattach the disk and finally delete it

Source: https://sysadmino.wordpress.com/2014/03/03/xenserver-does-not-reclaim-space-after-deleting-vdi-or-snapshot/


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