StarWind Resource Library

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

Published: March 13, 2017

INTRODUCTION

This technical paper describes how to successfully mount the StarWind LSFS snapshot in the ESXi. Snapshot mounting may come in handy when you need to restore the data that has been lost or deleted from the device. By default, all LSFS snapshots are mounted only in read-only mode. When mounting the snapshot in StarWind management console, a new separate StarWind device with a new Target is created. Having connected to the ESXi host, the snapshot tries to write its “signature” to the disc, but fails to do it, being read-only. As a result, an error occurs, and the snapshot doesn’t get mounted. To tackle this issue, LSFS has a pseudo read only – mode: a small WB cache that is never flushed. When the snapshot is created, the console sends “IsEsxCompatibleMode: Yes”, and the device rises to the ESXi compatible mode. This paper will cover three basic mounting scenarios:

• turning off the original device and keeping the existing signature;
• assigning a new signature (UUID);
• formatting the disk.

This guide is intended for experienced system administrators and IT professionals who would like to configure StarWind Virtual SAN solution. It provides detailed instructions on how to create and mount the LSFS snapshots in the ESXi. Please note that this document assumes that you’ve got an LSFS device created. If you don’t know how to do it, consult the StarWind Virtual SAN built-in Help or refer to the corresponding guide from the technical papers section on StarWind website.

A full set of up-to-date technical documentation can always be found here, or by pressing the Help button in the StarWind Management Console.

For any technical inquiries, please visit our online community, Frequently Asked Questions page, or use the support form to contact our technical support department.

Creating a Snapshot

PLEASE NOTE: a snapshot can be taken only after the original StarWind device is connected to the client (hypervisor) as a datastore.

1. Launch StarWind Management Console. Right click LSFS device you want and select Snapshot Manager from the pop-up menu.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

2. Click Create Snapshot button.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

3. Enter the snapshot name or leave it default. Click Create.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

Snapshot mounting in StarWind Console

1. Select the snapshot and click Mount Snapshot button.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

2. Leave the default cache settings and click Next.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

3. Leave the default settings and click Next.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

4. Click Create.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

5. Click Next.

6. Click Close after the device is created.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

3.1 The status of the selected snapshot is changed to Mounted.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

3.2 The new snapshot is available on the list of StarWind devices.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

Mounting the snapshot to the ESXi host

Mounting the snapshot with the existing signature

PLEASE NOTE: this option works only when the snapshot is directly connected to the ESXi host. So far, the snapshot cannot be properly mounted in the vCenter on the ESXi host due to the VMware known issue.

1. Right click the original device and Unmount it from the ESXi host.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

2. Click Add Storage.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

3. Select the LUN. The name of the original device the snapshot was taken from is displayed in the VMFS Label column.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

4. Select Keep the existing signature.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

5. Click Finish.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

6. The snapshot is successfully created.
WARNING: Once you have finished working with the snapshot, you need to unmount it from the ESXi host. DO NOT REMOVE THE SNAPSHOT! The delete operation will overwrite the device signature with zeros, and the snapshot will be no longer available for re-mounting!

Mounting the snapshot with a new signature

When mounting the snapshot with a new signature, ESXi assigns it a new UUIDand a new name and mounts it as a separate independent Datastore. The default format of the new name is snap-snapID-oldLabel, where oldLabel is the name of the original device.

1. Run the wizard and click Add Storage.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

2. Select the LUN. The name of the original device the snapshot was taken from is displayed in the VMFS Label column.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

3. Select Assign a new signature.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

4. The last page shows the new UUID the ESXi assigned to the mounted snapshot, which now is a separate Datastore. Click Finish.

StarWind Virtual SAN Working with StarWind LSFS Snapshots in ESXi

WARNING: Once you have finished working with the snapshot, you need to unmount it from the ESXi host. DO NOT REMOVE THE SNAPSHOT! The delete operation will overwrite the device signature with zeros, and the snapshot will be no longer available for re-mounting!

The second option – you can unmount the snapshot from the ESXi host in Starwind Console. To do this, right click the target and select Force remove Target from the pop-up menu.

Mounting the snapshot with full formatting

Format the disk option is available, but it makes little sense since the snapshots are ReadOnly. If you select this option, the ESXi will try to remove the file system from the ReadOnly snapshot, which will lead to an access error.

Working with multiple snapshots

Prior to mounting the snapshot in the ESXi, it must be mounted in the StarWind management console as a separate Target Device. The above-described interaction aspects of the ESXi and snapshots don’t allow mounting several snapshots of the Starwind device and connecting them to the ESXi host. Therefore, only one StarWind snapshot must be mounted for successful work with the ESXi!

The HA LSFS works in the same way as a usual LSFS, but one more condition is added: in case the already mounted snapshot resides on one of the StarWind nodes, it cannot be mounted on other nodes!

CONCLUSION

Keeping the existing signature and assigning a new one are two basic scenarios that allow successful mounting of the StarWind snapshot in the ESXi using the Add Storage wizard in the vSphere client. The first option, keeping the existing signature, requires the original device being unmounted from the ESXi host since connecting the snapshot with the same UUID can cause all kinds of issues. As you have seen, once the initial datastore is turned off, the mounted snapshot with the same signature can be brought online. The second option, assigning a new signature, allows creating a separate datastore as the hypervisor assigns it new technical identifiers different from those of the initial one.

To avoid all kinds of errors, it is highly recommended to mount only one snapshot of the StarWind device in the ESXi. In case of the HA LSFS, the snapshot can be mounted only on one of the nodes running the StarWind service.