Overview of Volume Migration

REST API Reference Guide for Virtual Storage Platform 5000, Virtual Storage Platform E Series, and Virtual Storage Platform G/F Series

Version
93-07-0x
90-09-0x
88-08-10
Audience
anonymous
Part Number
MK-98RD9014-17
Volume Migration is used to move data on a volume to another volume within the storage system (including a volume on an external storage system). Moving data to another volume is called migration.

Use Volume Migration to perform migration in situations such as the following:

  • When you want to migrate data from the old storage system when a new storage system is installed
  • When you want to migrate data with a low frequency of I/O operations to an external storage system
  • When you want to relocate data with a high frequency of I/O operations to a volume on a drive with a low usage rate or to a volume on a drive with high performance

The host can access data during migration. When migration is complete, the LDEV ID and the host I/O of the migration source volume are automatically swapped with those of the migration target volume. For this reason, the host can continue to access data after the migration by using the same path settings.

The following figures show the flow of data when migration is performed by using Volume Migration.

Before migration

I/O from the host is directed to the migration source volume. From the source volume and the target volume (the volume that was created for the purpose of migration), create a pair to be used for Volume Migration.

During migration

When migration is performed, data is copied from the source volume to the target volume. During migration, the host can read and write data online. If a write I/O operation from the host is performed while the data is being copied, only the differential data is copied to the target volume. Copy operations continue to be performed until all differential data has been copied.

Note:

There is an upper limit to the number of copy operations that can be performed, and the upper limit varies depending on the capacity of the source volume. If differential data still exists after the upper limit for the number of copy operations is exceeded, migration will fail. In this case, reduce the load from the host, and then perform migration again. Use a value of 50 IOPS or less as a reference value for the update I/O operations from the host.

When migration is complete

After the data is copied and the data on the source volume and the data on the target volume are fully synchronized, the LDEV ID and the host I/O of the source volume are swapped with those of the target volume. From the host, the volume and the path settings are the same as before the migration. The actual data, however, has been migrated to the volume that was prepared for migration.