On Wed, 2020-07-15 at 15:42 +0300, Nir Soffer wrote:

On Wed, Jul 15, 2020 at 3:12 PM Arsène Gschwind

<

<mailto:arsene.gschw...@unibas.ch>

arsene.gschw...@unibas.ch

> wrote:


Hi Nir,


I've followed your guide, please find attached the informations.

Thanks a lot for your help.


Thanks, looking at the data.


Quick look in the pdf show that one qemu-img info command failed:


---

lvchange -ay 
33777993-a3a5-4aad-a24c-dfe5e473faca/6197b30d-0732-4cc7-aef0-12f9f6e9565b


lvs 33777993-a3a5-4aad-a24c-dfe5e473faca/6197b30d-0732-4cc7-aef0-12f9f6e9565b

LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert

6197b30d-0732-4cc7-aef0-12f9f6e9565b

33777993-a3a5-4aad-a24c-dfe5e473faca -wi-a----- 5.00g


qemu-img info --backing-chain

/dev/33777993-a3a5-4aad-a24c-dfe5e473faca/6197b30d-0732-4cc7-aef0-12f9f6e9565b

qemu-img: Could not open

'/dev/33777993-a3a5-4aad-a24c-dfe5e473faca/8e412b5a-85ec-4c53-a5b8-dfb4d6d987b8':

Could not open '/dev/33777993-

a3a5-4aad-a24c-dfe5e473faca/8e412b5a-85ec-4c53-a5b8-dfb4d6d987b8': No

such file or directory

---


Maybe this lv was deactivated by vdsm after you activate it? Please

try to activate it again and

run the command again.


Sending all the info in text format in the mail message would make it

easier to respond.

I did it again with the same result, and the LV was still activated.

lvchange -ay 
33777993-a3a5-4aad-a24c-dfe5e473faca/6197b30d-0732-4cc7-aef0-12f9f6e9565b

lvs 33777993-a3a5-4aad-a24c-dfe5e473faca/6197b30d-0732-4cc7-aef0-12f9f6e9565b

  LV                                   VG                                   
Attr       LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert

  6197b30d-0732-4cc7-aef0-12f9f6e9565b 33777993-a3a5-4aad-a24c-dfe5e473faca 
-wi-a----- 5.00g

qemu-img info --backing-chain 
/dev/33777993-a3a5-4aad-a24c-dfe5e473faca/6197b30d-0732-4cc7-aef0-12f9f6e9565b

qemu-img: Could not open 
'/dev/33777993-a3a5-4aad-a24c-dfe5e473faca/8e412b5a-85ec-4c53-a5b8-dfb4d6d987b8':
 Could not open 
'/dev/33777993-a3a5-4aad-a24c-dfe5e473faca/8e412b5a-85ec-4c53-a5b8-dfb4d6d987b8':
 No such file or directory

lvs 33777993-a3a5-4aad-a24c-dfe5e473faca/6197b30d-0732-4cc7-aef0-12f9f6e9565b

  LV                                   VG                                   
Attr       LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert

  6197b30d-0732-4cc7-aef0-12f9f6e9565b 33777993-a3a5-4aad-a24c-dfe5e473faca 
-wi-a----- 5.00g


Sorry for the PDF, it was easier for me, but I will post everything in the mail 
from now on.



Arsene


On Tue, 2020-07-14 at 23:47 +0300, Nir Soffer wrote:


On Tue, Jul 14, 2020 at 7:51 PM Arsène Gschwind


<


<mailto:arsene.gschw...@unibas.ch>

arsene.gschw...@unibas.ch



wrote:



On Tue, 2020-07-14 at 19:10 +0300, Nir Soffer wrote:



On Tue, Jul 14, 2020 at 5:37 PM Arsène Gschwind



<



<mailto:arsene.gschw...@unibas.ch>

arsene.gschw...@unibas.ch





wrote:




Hi,




I running oVirt 4.3.9 with FC based storage.



I'm running several VM with 3 disks on 3 different SD. Lately we did delete a 
VM Snapshot and that task failed after a while and since then the Snapshot is 
inconsistent.



disk1 : Snapshot still visible in DB and on Storage using LVM commands



disk2: Snapshot still visible in DB but not on storage anymore (It seems the 
merge did run correctly)



disk3: Snapshot still visible in DB but not on storage ansmore (It seems the 
merge did run correctly)




When I try to delete the snapshot again it runs forever and nothing happens.




Did you try also when the vm is not running?



Yes I've tried that without success




In general the system is designed so trying again a failed merge will complete



the merge.




If the merge does complete, there may be some bug that the system cannot



handle.




Is there a way to suppress that snapshot?



Is it possible to merge disk1 with its snapshot using LVM commands and then 
cleanup the Engine DB?




Yes but it is complicated. You need to understand the qcow2 chain



on storage, complete the merge manually using qemu-img commit,



update the metadata manually (even harder), then update engine db.




The best way - if the system cannot recover, is to fix the bad metadata



that cause the system to fail, and the let the system recover itself.




Which storage domain format are you using? V5? V4?



I'm using storage format V5 on FC.



Fixing the metadata is not easy.



First you have to find the volumes related to this disk. You can find


the disk uuid and storage


domain uuid in engine ui, and then you can find the volumes like this:



lvs -o vg_name,lv_name,tags | grep disk-uuid



For every lv, you will have a tag MD_N where n is a number. This is


the slot number


in the metadata volume.



You need to calculate the offset of the metadata area for every volume using:



    offset = 1024*1024 + 8192 * N



Then you can copy the metadata block using:



    dd if=/dev/vg-name/metadata bs=512 count=1 skip=$offset


conv=skip_bytes > lv-name.meta



Please share these files.



This part is not needed in 4.4, we have a new StorageDomain dump API,


that can find the same


info in one command:



    vdsm-client StorageDomain dump sd_id=storage-domain-uuid | \


        jq '.volumes | .[] | select(.image=="disk-uuid")'



The second step is to see what is the actual qcow2 chain. Find the


volume which is the LEAF


by grepping the metadata files. In some cases you may have more than


one LEAF (which may


be the problem).



Then activate all volumes using:



    lvchange -ay vg-name/lv-name



Now you can get the backing chain using qemu-img and the LEAF volume.



    qemu-img info --backing-chain /dev/vg-name/lv-name



If you have more than one LEAF, run this on all LEAFs. Ony one of them


will be correct.



Please share also output of qemu-img.



Once we finished with the volumes, deactivate them:



    lvchange -an vg-name/lv-name



Based on the output, we can tell what is the real chain, and what is


the chain as seen by


vdsm metadata, and what is the required fix.



Nir




Thanks.




Thanks for any hint or help.



rgds , arsene




--




Arsène Gschwind <



<mailto:arsene.gschw...@unibas.ch>

arsene.gschw...@unibas.ch







Universitaet Basel



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--


Arsène Gschwind <

<mailto:arsene.gschw...@unibas.ch>

arsene.gschw...@unibas.ch

>

Universitaet Basel


--

Arsène Gschwind
Fa. Sapify AG im Auftrag der universitaet Basel
IT Services
Klinelbergstr. 70 | CH-4056 Basel | Switzerland
Tel: +41 79 449 25 63 | http://its.unibas.ch
ITS-ServiceDesk: support-...@unibas.ch<mailto:support-...@unibas.ch> | +41 61 
267 14 11
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