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Virtualize your Migration

by Hu Yoshida on Jan 24, 2009

Chris Evans posted a great blog about the problems of migration for large storage arrays that are getting larger. He calculated that it would take 6 months to migrate a 125TB array that is connected to 250 servers. This would require a weekly migration schedule of 5TB and 10 servers a week for one FTE ( Full Time Employee). That would assume that you could dictate migration windows and that data was not inter-tangled between applications and servers.

Some of our customers tell us that it takes about $10,000 of burdened cost per TB to migrate from one storage frame to another.  Using this number, a 125 TB storage array could cost $1,250,000 to migrate to another storage array. This is not hard to imagine since you would have two storage arrays along with additional SAN infrastructure sitting on the floor during the 6 months. You would also have duplicate license charges and maintenance charges on the older box if its warrantee has expired. There could also be business impact costs due to the disruption of migration windows.

Chris makes several recommendations to ease the effort of storage migration. One of them is storage virtualization. Storage virtualization can reduce the disruption of migration by enabling the servers to resume operation with a virtualized interface to their storage while the data is being migrated in the background.

 I visited a bank in North Carolina who had received a USP V on a Friday after noon. On Saturday they transferred 75 volumes in 45 min by inserting the USP V between the server and the older storage array and discovering the LUNs on the older array through the cache of the USP V.  As soon as this was done they began their application testing on the USP V while the data was being moved in the background. On Monday morning they switched their on line banking application to the new USP V.  In one weekend they were able to do a migration that could have taken a month or more without virtualization..

If you are about to purchase a new storage array, consider the cost of migration and the savings that could result from an investment in storage virtualization.

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Comments (2 )

William Piper on 24 Jan 2009 at 11:28 pm

What is the difference between this type of migration, and a hot Open Replicator migration? Utilizing Open Replicator in conjunction with Powerpath PPME you could even do this without the 45 min outage the USP V migration required.

Since the wonderful word “virtualization” was mentioned, I must ask how the Hitachi Dynamic Provisioning vitualization feature can be taken advantage of in this scenario? Now that the 75 volumes are in the new USP V array how do you convert them to “thin” volumes/luns?

Hu Yoshida on 01 Feb 2009 at 8:44 pm

Hello William, I am not as familar with Open replicator, but from the literature it appears to provide the same capability for migration of data from selected heterogeneous storage systems.
Since the USP V uses virtualization for the migration we can combine migration with other services. For conversion to “thin” volumes, we migrate the external storage into a Dynamic Provisioning pool. As we fill up the pages in the pool, we detect “zero” pages and “thin” them out during the migration.

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