Replacing/Moving a Storage Source in Virtual Disks

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Operation Comparison

The Replace operation is similar to the Move operation. In each operation, one of the storage sources in a multi-copy virtual disk (comprised of two or more separate storage sources on different servers) will be replaced by or moved to a new storage source.

The main differences between the operations are:

Replace operation
- Requires a full recovery and does not maintain high availability during the process.
- Replaces the original storage sources (pool or pass-through) in the virtual disks with new storage sources (pool or pass-through) from the same server.
- Not supported for single or dual virtual disks.
Move operation
- Requires a log recovery and maintains high availability during most of the process.
- Moves the original storage sources (pool or pass-through) in the virtual disks to another pool on the same server. Dual virtual disks can be moved to a different server that shares the same pool.
- Not supported for single virtual disks.

Refer to the appropriate section for details.

Replacing a Storage Source

The Replace operation replaces one original storage source (pool or pass-through) in the multi-copy virtual disks with a new storage source (pool or pass-through) from the same server. When the original storage source is replaced, all paths are adjusted to use the new storage source and data on the new storage source is synchronized with a full recovery.

If the virtual disk is served to a host and has functional paths to two servers, the storage source can be replaced without the host losing access to the virtual disk.

This option is only available if the storage source is eligible for replacement. The Replace operation is not available for single or dual virtual disks. (See Moving a Storage Source for dual virtual disks.).
The Replace operation cannot be performed on storage sources when the mirror partner is not healthy.
Adequate space must be available in the source you are using as a replacement.
A storage source from a virtual disk with a 512 B sector size must be replaced with a storage source from a pool with a 512 B sector size. A storage source from a virtual disk with a 4 K sector size can be replaced by a storage source from a pool with either 4 K or 512 B sector size.
Sector sizes of all storage sources being replaced in the same operation must be the same; either all 512 B or all 4 KB.
Storage source replacement is only allowed from the same DataCore Server.
(To replace a storage source from a different DataCore Server, virtual disks can be split, and then remirrored with a storage source from a different server. See Converting Virtual Disks to Another Type.)
Snapshots and rollbacks created from the storage source will be deleted if the storage source is replaced.
More than one storage source can be replaced in a virtual disk, but only one storage source can be replaced at a time and the virtual disk must recover and be in Up-to-date status before the other source can be replaced.
Replacing the storage source of a virtual disk in a replication is not allowed.
Replacing the storage source of a CDP-enabled virtual disk will disable the CDP feature if the side which has the history log is replaced. After the virtual disk has recovered and data is up-to-date, the CDP can be enabled again. Replacing the side which does not also have the history log will not affect CDP for the virtual disk.
During the replace operation, if the new pool/disks become unavailable and then become available again, recovery will start again. If the original pool/disks become unavailable, then the replace operation occurs, when the original pool/disks become available again, auto-generated virtual disks may be created in the configuration for those storage sources that were replaced. These auto-generated virtual disks can be deleted (after verifying that the mirrors are healthy after the replace) in order to reclaim the space used in the disk pool.

To replace a storage source:

This operation can also be performed on multiple virtual disks selected from the Virtual Disks List.

In the Virtual Disk Details page>Info tab, click Replace next to the source to replace.
Storage sources can also be replaced in the Summary of a virtual disk in the Virtual Disks List
In the Replace Storage Source dialog box, select the source type for the new source.
In the list, select the pool or pass-through disk to use as a replacement.
Click Replace.
A confirmation message will appear; read the message carefully and affirm the operation to continue.
Monitor the virtual disk and data status from the Status column in the Virtual Disk List. The status of the replace operation will reflect In recovery and display the percentage complete. Status can also be monitored in the Virtual Disk Details page>Info tab for individual virtual disks. Do not perform additional configuration changes until the status is Healthy.

Moving a Storage Source

The Move operation copies data from one storage source to another. The operation can "move" one storage source of a multi-copy virtual disk to a pool on the same DataCore Server. The Move operation can also "move" one storage source of a dual virtual disk to another server that shares the same pool, in other words, the virtual disk can be "moved across server". This operation is performed while maintaining high availability during most of the process. The storage source to be moved can come from a pool or pass-through disk, but the new storage source can only be created from a disk pool. After the storage source has been moved, all paths are adjusted.

This operation is useful for migrating virtual disk SAUs from one pool to another on the same server, as well as migrating to a different server through a shared pool. For instance, assume that a server group consists of three servers (SSY1, SSY2, and SSY3) and all three servers share a pool (SharedPool1). A dual virtual disk is created from SSY1 and SSY2 using SharedPool1. The storage source from SSY2 could be moved to SSY3, so that the dual virtual disk would have storage sources from SSY1 and SSY3. In this manner, data can be moved from one server to another in the server group. In addition, the storage source could then be moved from SharedPool1 to a non-shared pool on SSY3. Using the Move operation to migrate a storage source to a different server through a shared pool requires a Shared Multi-port Array license.

The entire process may take several hours depending on the amount of allocated SAUs, amount of I/O from the host during the operation, and the speed of the back-end physical disks in the pool. High availability will be maintained during the process except for the minimal time when the actual swap of the storage source in the virtual disk is taking place. During this time, host access will be disabled on the storage source being moved and a failover to the other server will occur. (If the mirror partner is inaccessible and the failover cannot take place, the move operation will be aborted.) After the process is complete, a log recovery will take place to synchronize the mirrors—a full recovery is not necessary.

This operation is only supported for multi-copy or dual virtual disks; not single virtual disks. The new storage source must be a pool on the same server as the original storage source, or a pool shared by the same server. The move operation is not supported for virtual disks created from shared pools that have mirrored physical disks. The Move operation is not applicable to the inactive (host access disabled) storage source in the 3-copy virtual disk, but it can be replaced.
The Move operation cannot be performed on storage sources where the mirror partner is not healthy.
Ensure sufficient free space exists on the new pool to accommodate the SAUs being moved. If sufficient space does not exist, the move will be cancelled.
A storage source from a virtual disk with a 512 B sector size must be moved to another pool with a 512 B sector size. A storage source from a virtual disk with a 4 K sector size can be moved to a pool with either 4 K or 512 B sector size.
Sector sizes of all storage sources being moved in the same operation must be the same; either all 512 B or all 4 KB.
Paths must be available or the move will be cancelled. Virtual disks using redundant paths will be recreated with redundant paths if sufficient paths exist. If insufficient paths exist to create redundant paths, the move will occur and an alert will be posted that redundant paths could not be created.
In the case of multi-copy virtual disks, snapshots and rollbacks created from the storage source being moved will be deleted. In the case of dual virtual disks, the operation is not supported if snapshots and rollbacks are created from the storage source to be moved.
This operation is not supported for virtual disks that are the source of a replication or are enabled for sequential storage.
Moving the source of a CDP-enabled virtual disk will disable the CDP feature if the side which has the history log is being moved. After the virtual disk has recovered and data is up-to-date, data protection can be enabled again. Moving the side which does not also have the history log will not affect data protection for the virtual disk.
During the move operation, if the new pool/disks become unavailable the move operation will be aborted. When the pool or disks become available again, auto-generated virtual disks may be created in the configuration for those storage sources that were moved. These auto-generated virtual disks may or may not have data depending on when the backend went unavailable. Check to ensure that the virtual disks that were moved have complete data, then the auto-generated virtual disks can be deleted to reclaim the pool space.
When the Move operation completes, writes to the side of the virtual disk which was not moved will be briefly held off while the mirror path is being redirected. As such, a Move may result in a brief temporary loss of access to hosts.

To move the storage source:

This operation can also be performed on multiple virtual disks selected from the Virtual Disks List.

In the Virtual Disk Details page>Info tab, click Move next to the source to move.
In the Move Storage Source dialog box, select the DataCore Server to use for the new source.
In the list, select the pool to use.
Click Move.
A confirmation message will appear; read the message carefully and affirm the operation to continue.
Monitor the virtual disk and data status from the Status column in the Virtual Disk List. During the swap of the storage source, the status will reflect Moving and display the percentage complete. Status can also be monitored in the Virtual Disk Details page>Info tab for individual virtual disks. Do not perform additional configuration changes until the status is Healthy.

To cancel the operation:

In a panel or any Virtual Disks List, right-click on the virtual disk and select Abort Move.
Alternatively, the operation can also be aborted from the progress bar from the Virtual Disk Details page>Info tab or the Virtual Disks List>Virtual Disk Summary.