Timestamp lost in Continuous Replication

ph7

I did get a snapshot at one of the CR VM's with the 449e7 version.
I don't with 5bdd7

florent

@ph7 yes this is expected even if we did not have time to communicate on this yet : https://github.com/vatesfr/xen-orchestra/pull/9524

the goal is to have more symmetry between the source ( on VM with snapshots ) and the replica ( on VM with snapshots) . The end goal is to use this to be able to reverse a PRD , and to allow advanced scenarii like VM on edge site => replica on center site => backup on central servers

but it should not do full backups, it should respect the delta / full chain

fbeauchamp opened this pull request in vatesfr/xen-orchestra

closed feat(backups): symetrical backups #9524

Pilow

@florent Florent, I could see the benefits of unified VM name, but could you at least push the timestamp in a note on the VM ?
it is important to know wich timestamp a replica VM is, in order to choose failover option wisely

florent

@Pilow the timestamp is on the snapshot, but you're right, we can add a note on the VM with the last replications informations

note that the older VMs replicated will be purged when we are sure they don't have any usefull data , so you will have only one VM replicated , wuth multiple snapshots

Pilow

@florent ho nice
we had as many "VMs with a timestamp in the name" as number of REPLICAs, and multiple snapshot on source VM
now we have "one Replica VM with multiple snapshots" ? Veeam-replica-style...
do multiple snapshots persists on source VM too ?

if it's true, that's nice on the concept.

but when your replica is over lvmoiscsi not so nice

ps : i didnt upgrade to last XOA/XCP patchs yet

florent

@Pilow

we had as many "VMs with a timestamp in the name" as number of REPLICAs, and multiple snapshot on source VM
now we have "one Replica VM with multiple snapshots" ? Veeam-replica-style...

we didn't look at veeam , but it's reassuring to see that we converge toward the solutions used elsewhere

it shouldn't change anything on the source
I am currently doing more test to see if we missed something

edit: as an additional beenfits it should use less space on target it you have a retention > 1 since we will only have one active disk

kratos

Hello everyone,

I’m not sure if my information is useful, but I’m experiencing the same problem. I am using continuous replication between two servers with a retention of 4.
Previously, four VM replicas were created, each with a timestamp in the name. With the current version, four VMs are created with identical names.

My environment:
XO: from source commit 598ab
xcp-ng: 8.3.0 with the latest patches

My backup job:
Name of backup job: replicate_to_srv002
Source server: srv003
Target server: srv002
VM name: privat
Retention: 4

Result on the target server:
4 VMs with the name "[XO Backup replicate_to_srv002] privat - replicate_to_srv002", where only the newest one contains a snapshot named: "privat - replicate_to_srv002 - (20260318T083542Z)"

Additionally, full backups are created on every run of the backup job, and no deltas are being used.

If I can help with any additional information, I’d be happy to do so.

Best regards,
Simon

Pilow

@kratos @florent shouldn't he have one VM with 4 snapshots ? and delta replicas between each snap ?

kratos

@Pilow
actually it looks like this:

edit:

Log of last run:

{
  "data": {
    "mode": "delta",
    "reportWhen": "failure"
  },
  "id": "1773822934377",
  "jobId": "a95ac100-0e20-49c5-9270-c0306ee2852f",
  "jobName": "replicate_to_srv002",
  "message": "backup",
  "scheduleId": "1014584a-228c-4049-8912-51ab1b24925a",
  "start": 1773822934377,
  "status": "success",
  "infos": [
    {
      "data": {
        "vms": [
          "224a73db-9bc6-13d6-cc8e-0bf22dbede73"
        ]
      },
      "message": "vms"
    }
  ],
  "tasks": [
    {
      "data": {
        "type": "VM",
        "id": "224a73db-9bc6-13d6-cc8e-0bf22dbede73",
        "name_label": "privat"
      },
      "id": "1773822936247",
      "message": "backup VM",
      "start": 1773822936247,
      "status": "success",
      "tasks": [
        {
          "id": "1773822937378",
          "message": "snapshot",
          "start": 1773822937378,
          "status": "success",
          "end": 1773822940361,
          "result": "d0ba1483-f5ae-ce72-fb4f-dbd9eafbf272"
        },
        {
          "data": {
            "id": "8205e6c4-4d8f-69d9-6315-9ee89af8e307",
            "isFull": true,
            "name_label": "Local storage",
            "type": "SR"
          },
          "id": "1773822940361:0",
          "message": "export",
          "start": 1773822940361,
          "status": "success",
          "tasks": [
            {
              "id": "1773822942354",
              "message": "transfer",
              "start": 1773822942354,
              "status": "success",
              "tasks": [
                {
                  "id": "1773823497635",
                  "message": "target snapshot",
                  "start": 1773823497635,
                  "status": "success",
                  "end": 1773823500290,
                  "result": "OpaqueRef:53bceb07-a69c-504d-e824-28f5384cb763"
                }
              ],
              "end": 1773823500290,
              "result": {
                "size": 61941481472
              }
            },
            {
              "id": "1773823501512",
              "message": "health check",
              "start": 1773823501512,
              "status": "success",
              "tasks": [
                {
                  "id": "1773823501515",
                  "message": "cloning-vm",
                  "start": 1773823501515,
                  "status": "success",
                  "end": 1773823504720,
                  "result": "OpaqueRef:43e9644f-fc99-963a-4a54-da3b845e823b"
                },
                {
                  "id": "1773823504722",
                  "message": "vmstart",
                  "start": 1773823504722,
                  "status": "success",
                  "end": 1773823545662
                }
              ],
              "end": 1773823549312
            }
          ],
          "end": 1773823549312
        }
      ],
      "end": 1773823549319
    }
  ],
  "end": 1773823549319
}

florent

@kratos @pilow is it possible that your replications are in the same pool ?

kratos

@florent
Yes, that is absolutely correct. I have a pool with two members without shared storage. Some VMs run on the master, and some on the second pool member. I replicate between the pool members so that, if necessary, I can start the VMs on the other member. This may not be best practice.

florent

@kratos you probably heard the sound of my head hitting my desk when I found the cause
the fix is in review, you will be able to use it in a few hours

kratos

@florent
I’m a developer myself, so I can totally relate—just when you think everything is working perfectly, someone like me comes along
I’m really glad I could help contribute to finding a solution, and I’ll report back once I’ve tested the new commit. Thanks a lot for your work.

However, this does raise the question for me: is my use case for continuous replication really that unusual?

florent

@kratos no, it's not that rare. I even saw in the wild replication on the same storage (wouldn't recommend it , though )

the cross pool replication is a little harder since the objects are each split on their own xen api, so the calls must be routed to the right one
We tested the harder part, not the mono xapi case

Pilow

@kratos said:

This may not be best practice.

in a two hosts pool, if your replicated VMs live on the Master, and it's gone, you won't be able to start the replicated VMs

you will first need to transition slave to master

indeed CR is better to another pool