ZStack 3.10.0>Tutorials>Private Cloud>Upgrade Tutorial>Upgrade Considerations

Upgrade Considerations

Specific considerations apply when you upgrade ZStack Cloud. The following considerations help you with the upgrade:

During the Cloud upgrade, you cannot access the management node or apply for resources such as VM instances and volumes. Therefore, we recommend that you perform upgrade during off-peak hours.
After the management node is upgraded, the Cloud will reconnect all hosts, primary storages, backup storages, and routers, and automatically upgrade related resources. During the reconnection, the VM instances, volumes, and other related resources cannot be operated.
If the upgrade is interrupted due to an exception occurred during the Cloud upgrade, perform the upgrade again after this issue is troubleshooted.

The libvirt version can be automatically upgraded during the upgrade of ZStack. Specifically, if you are using c74 ISO and QEMU 2.9, the libvirt version will be automatically upgraded to 4.9.0.
Note:
- If you deployed the Cloud with an open-source Ceph distributed storage and enabled Cephx (the Ceph authentication protocol), an error might be reported during CD-ROM hot swapping on a VM instance. This error is caused because the new libvirt version currently does not support hot swapping. For more information, contact the official technical support for help.
- From ZStack 3.2.0, the supported format of shared volumes is changed to raw. Therefore, the format of shared volumes created in a Shared Block primary storage is changed to raw. In this case, you cannot create snapshots for or resize the shared volumes. In addition, when the attached VM instances are in the running state, you cannot create images for these shared volumes. However, the preceding restrictions will be lifted, and more features will be provided in later versions of ZStack. For more information, follow our official website for updates.
- You can disable libvirt auto upgrade as needed. Method:
  Go to /usr/local/zstack/apache-tomcat/webapps/zstack/WEB-INF/classes/zstack.properties, and set the following parameter in zstack.properties:
```
updatePkgWhenConnect = false
# Disable libvirt auto upgrade. The default value is true.
```
  Restart the management node for the setting to take effect.
From version 3.7.1, ZStack provides two ISO versions: c76 and c74, either of whose repos are compatible in both versions. When you upgrade the Cloud, note that:
- Version 3.7.1 and later versions will no longer provide c72 ISO for you to install and deploy new Clouds. However, you can upgrade your existing c72 ISO to the latest version. For information about capacity expansion or system upgrade, contact the official technical support.
- From 3.7.1, the local repo in c72 is redirected to c74. If you upgrade your Cloud offline, obtain c74 ISO to replace the local repo.

Next Chapter:Preparations