Ok. Thank you, I appreciate it!

I don't know if this helps from the SMlog

[15:18 iahost-xcpng-server2 ~]# grep -i "coalesce" /var/log/SMlog
Jul  8 14:32:53 iahost-xcpng-server2 SM: [31275] Aborting GC/coalesce
Jul  8 14:33:00 iahost-xcpng-server2 SM: [31789] Entering doesFileHaveOpenHandles with file: /dev/mapper/VG_XenStorage--88d7607c--f807--3b06--6f70--2dcb319d97ea-coalesce_8241ba22--3125--4f45--b3b1--254792a525c7_1
Jul  8 14:33:00 iahost-xcpng-server2 SM: [31789] Entering findRunningProcessOrOpenFile with params: ['/dev/mapper/VG_XenStorage--88d7607c--f807--3b06--6f70--2dcb319d97ea-coalesce_8241ba22--3125--4f45--b3b1--254792a525c7_1', False]
Jul  8 14:33:00 iahost-xcpng-server2 SM: [31789] ['/sbin/dmsetup', 'remove', '/dev/mapper/VG_XenStorage--88d7607c--f807--3b06--6f70--2dcb319d97ea-coalesce_8241ba22--3125--4f45--b3b1--254792a525c7_1']
Jul  8 14:59:34 iahost-xcpng-server2 SMGC: [20458] Coalesced size = 316.035G
Jul  8 14:59:34 iahost-xcpng-server2 SMGC: [20458] Coalesce candidate: *8241ba22[VHD](600.000G//88.477G|n) (tree height 5)
Jul  8 14:59:35 iahost-xcpng-server2 SMGC: [20458] Coalesced size = 316.035G
Jul  8 14:59:35 iahost-xcpng-server2 SMGC: [20458] Coalesce candidate: *8241ba22[VHD](600.000G//88.477G|a) (tree height 5)
Jul  8 14:59:35 iahost-xcpng-server2 SM: [20458] ['/sbin/lvremove', '-f', '/dev/VG_XenStorage-88d7607c-f807-3b06-6f70-2dcb319d97ea/coalesce_8241ba22-3125-4f45-b3b1-254792a525c7_1']
Jul  8 14:59:35 iahost-xcpng-server2 SM: [20458] ['/sbin/dmsetup', 'status', 'VG_XenStorage--88d7607c--f807--3b06--6f70--2dcb319d97ea-coalesce_8241ba22--3125--4f45--b3b1--254792a525c7_1']
Jul  8 14:59:36 iahost-xcpng-server2 SMGC: [20458] Coalesced size = 316.035G
Jul  8 14:59:36 iahost-xcpng-server2 SMGC: [20458] Coalesce candidate: *8241ba22[VHD](600.000G//88.477G|a) (tree height 5)
Jul  8 14:59:36 iahost-xcpng-server2 SM: [20458] ['/sbin/lvcreate', '-n', 'coalesce_8241ba22-3125-4f45-b3b1-254792a525c7_1', '-L', '4', 'VG_XenStorage-88d7607c-f807-3b06-6f70-2dcb319d97ea', '--addtag', 'journaler', '-W', 'n']
Jul  8 15:01:41 iahost-xcpng-server2 SMGC: [20458] Coalesced size = 316.035G
Jul  8 15:02:11 iahost-xcpng-server2 SMGC: [20458]   Running VHD coalesce on *8241ba22[VHD](600.000G//88.477G|a)
Jul  8 15:02:11 iahost-xcpng-server2 SM: [22617] ['/usr/bin/vhd-util', 'coalesce', '--debug', '-n', '/dev/VG_XenStorage-88d7607c-f807-3b06-6f70-2dcb319d97ea/VHD-8241ba22-3125-4f45-b3b1-254792a525c7']

What does this mean exactly? When will this happen? I'm sorry I am very nervous.

I deleted the snapshot from this one vm.

However, that one remains in the list on here:

@olivierlambert Dang ok. I waited a few minute then clicked the Connect in XOA for that host and it connected. Not sure what to do really.

I rebooted the pool master. Even though it looks like it came up ok it is not connected to storage. In xcp-ng center it is showing a red X for the SR and this is the errors in dmesg.

[Tue Jul  8 14:43:19 2025] Loading iSCSI transport class v2.0-870.
[Tue Jul  8 14:43:19 2025] iscsi: registered transport (tcp)
[Tue Jul  8 14:43:20 2025] scsi host7: iSCSI Initiator over TCP/IP
[Tue Jul  8 14:43:20 2025] scsi 7:0:0:1: Direct-Access     SYNOLOGY Storage          4.0  PQ: 0 ANSI: 5
[Tue Jul  8 14:43:20 2025] scsi 7:0:0:1: alua: supports implicit TPGS
[Tue Jul  8 14:43:20 2025] scsi 7:0:0:1: alua: device naa.60014059c706a83d1e77d47a8da5c5d1 port group 0 rel port 1
[Tue Jul  8 14:43:20 2025] sd 7:0:0:1: Attached scsi generic sg1 type 0
[Tue Jul  8 14:43:20 2025] sd 7:0:0:1: alua: transition timeout set to 60 seconds
[Tue Jul  8 14:43:20 2025] sd 7:0:0:1: alua: port group 00 state A non-preferred supports TOlUSNA
[Tue Jul  8 14:43:25 2025] sd 7:0:0:1: [sdb] 26109542400 512-byte logical blocks: (13.4 TB/12.2 TiB)
[Tue Jul  8 14:43:25 2025] sd 7:0:0:1: [sdb] Write Protect is off
[Tue Jul  8 14:43:25 2025] sd 7:0:0:1: [sdb] Mode Sense: 43 00 10 08
[Tue Jul  8 14:43:25 2025] sd 7:0:0:1: [sdb] Write cache: enabled, read cache: enabled, supports DPO and FUA
[Tue Jul  8 14:43:25 2025] sd 7:0:0:1: [sdb] Attached SCSI disk
[Tue Jul  8 14:43:26 2025] sd 7:0:0:1: [sdb] Synchronizing SCSI cache
[Tue Jul  8 14:43:32 2025] Buffer I/O error on dev sdb, logical block 3263692798, async page read
[Tue Jul  8 14:43:32 2025] scsi 7:0:0:1: alua: Detached
[Tue Jul  8 14:43:40 2025] scsi host7: iSCSI Initiator over TCP/IP
[Tue Jul  8 14:43:40 2025] scsi 7:0:0:1: Direct-Access     SYNOLOGY Storage          4.0  PQ: 0 ANSI: 5
[Tue Jul  8 14:43:40 2025] scsi 7:0:0:1: alua: supports implicit TPGS
[Tue Jul  8 14:43:40 2025] scsi 7:0:0:1: alua: device naa.60014059c706a83d1e77d47a8da5c5d1 port group 0 rel port 1
[Tue Jul  8 14:43:40 2025] sd 7:0:0:1: Attached scsi generic sg1 type 0
[Tue Jul  8 14:43:40 2025] sd 7:0:0:1: alua: transition timeout set to 60 seconds
[Tue Jul  8 14:43:40 2025] sd 7:0:0:1: alua: port group 00 state A non-preferred supports TOlUSNA
[Tue Jul  8 14:43:46 2025] sd 7:0:0:1: [sdb] 26109542400 512-byte logical blocks: (13.4 TB/12.2 TiB)
[Tue Jul  8 14:43:46 2025] sd 7:0:0:1: [sdb] Write Protect is off
[Tue Jul  8 14:43:46 2025] sd 7:0:0:1: [sdb] Mode Sense: 43 00 10 08
[Tue Jul  8 14:43:46 2025] sd 7:0:0:1: [sdb] Write cache: enabled, read cache: enabled, supports DPO and FUA
[Tue Jul  8 14:43:49 2025] ldm_validate_partition_table(): Disk read failed.
[Tue Jul  8 14:43:49 2025]  sdb: unable to read partition table
[Tue Jul  8 14:43:49 2025] sd 7:0:0:1: [sdb] Attached SCSI disk
[Tue Jul  8 14:43:49 2025] sd 7:0:0:1: [sdb] Synchronizing SCSI cache
[Tue Jul  8 14:43:49 2025] scsi 7:0:0:1: alua: Detached

So even taking Vinchin out of the picture for now, I am still worried that xcp-ng will run the Garbage Collection and disconnect the ST, brining the VM down again.

Just keeps bouncing over and over

Is that due to the Master being disconnected from the SR. That is the one I was referring to in my previous Topic post "Pool Master".

@olivierlambert I did that on one and noticed a task API call: sr.scan I opened the raw log and seeing errors. AttachedSR Scan Errors.txt

Sorry I'm just a bit confused because it is showing no snapshots on the VM view