Re: [pve-devel] [PATCH qemu-server 14/14] qcow2: add external snapshot support

["DERUMIER, Alexandre via pve-devel" <pve-devel@lists.proxmox.com>]

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From: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
To: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>, "f.gruenbichler@proxmox.com" <f.gruenbichler@proxmox.com>
Subject: Re: [pve-devel] [PATCH qemu-server 14/14] qcow2: add external snapshot support
Date: Wed, 14 May 2025 12:56:05 +0000
Message-ID: <65c16a4b13391e8a6fc77bc4db961f9e895e52e5.camel@groupe-cyllene.com>


>>I'll continue some testing with the dir part (I thought LVM might be
>>more interesting to run into performance issues/.. ;))
>>
>>one thing that I already noticed is that snapshot images are listed
>>like
>>regular images:
>>$ pvesm list extsnapdir
>>Volid                                          Format  >>Type       
Size VMID
>>extsnapdir:555/snap-first-vm-555-disk-0.qcow2  qcow2   images   
>>1073741824 555
extsnapdir:555/snap-second-vm-555-disk-0.qcow2 qcow2   images   
1073741824 555
extsnapdir:555/vm-555-disk-0.qcow2             qcow2   images   
1073741824 555


arf, this don't happen on lvm 

# lvs
  LV                               VG      Attr       LSize   Pool
Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lvmthin                          lvmthin twi-aotz--  97.87g         
0.00   1.61                            
  data                             pve     twi-a-tz-- <29.75g         
0.00   1.58                            
  root                             pve     -wi-ao----  29.87g         
  swap                             pve     -wi-ao----   8.00g         
  base-10002-disk-0                test    -ri-a-----   1.00g         
  base-10002-disk-1                test    -ri-a-----   1.00g         
  snap-snap1-vm-1000-disk-2.qcow2  test    -wi-a-----   1.00g         
  snap-snap1-vm-10000-disk-0.qcow2 test    -wi-a-----   1.00g         
  snap-snap1-vm-10000-disk-6.qcow2 test    -wi-ao----   1.00g         
  snap-snap1-vm-10001-disk-0.qcow2 test    -wi-a-----   1.00g         
  snap-snap1-vm-10001-disk-1.qcow2 test    -wi-a-----   1.00g         
  snap-snap1-vm-10001-disk-2.qcow2 test    -wi-a-----   1.00g         
  snap-snap1-vm-10001-disk-3.qcow2 test    -wi-a-----   1.00g         
  snap-snap2-vm-10000-disk-1.qcow2 test    -wi-a-----   1.00g         
  snap-snap2-vm-10000-disk-2.qcow2 test    -wi-a-----   1.00g         
  snap-snap2-vm-10000-disk-3.qcow2 test    -wi-a-----   1.00g         
  snap-snap2-vm-10000-disk-4.qcow2 test    -wi-a-----   1.00g         
  snap-snap2-vm-10000-disk-5.qcow2 test    -wi-a-----   1.00g         
  snap-snap2-vm-10000-disk-6.qcow2 test    -wi-a-----   1.00g         
  snap-snap2-vm-110-disk-0.qcow2   test    -wi-a----- <20.10g         
  vm-1000-disk-0.qcow2             test    -wi-a-----   1.00g         
  vm-1000-disk-1.qcow2             test    -wi-a-----   1.00g         
  vm-10000-disk-6.qcow2            test    -wi-ao----   1.00g         
  vm-101-disk-0.qcow2              test    -wi-a-----   1.00g         
  vm-101-disk-1.qcow2              test    -wi-a-----   1.00g         
  vm-101-disk-2.qcow2              test    -wi-a-----   2.00g         
  vm-108-disk-0                    test    -wi-ao----   1.00g         
root@proxmoxdev1:~# pvesm list lvmtest2
Volid                          Format  Type            Size VMID
lvmtest2:vm-1000-disk-0.qcow2  raw     images    1077936128 1000
lvmtest2:vm-1000-disk-1.qcow2  raw     images    1077936128 1000
lvmtest2:vm-10000-disk-6.qcow2 raw     images    1077936128 10000
lvmtest2:vm-101-disk-0.qcow2   raw     images    1073741824 101
lvmtest2:vm-101-disk-1.qcow2   raw     images    1073741824 101
lvmtest2:vm-101-disk-2.qcow2   raw     images    2147483648 101
lvmtest2:vm-108-disk-0         raw     images    1073741824 108




>>>so we definitely still need to find a way to encode/store those
>>which makes
>>>the snapshot images properly separate from the "main" ones..

I would like to have something like vm-100-disk-0@snap1.qcow2 , to
match zfs|ceph internal names. (or another separator)

but I don't known if this seperator character is allowed on every
storage, and could not used currently or conflict with internal snap ?

AFAIK, lvm allowed characters are:


"A" through "Z"
"a" through "z"
"0" through "9"
"_" (the underscore)
"-" (the minus sign)
"." (the period)


(maybe underscore ? vm-100-disk-0_snap1.qcow2  ?)


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