Storage Virtualization Benefits

Storage virtualization is an emerging technology that creates logical abstractions of physical storage systems. With the help of Storage virtualization, the storage disks from multiple vendors can be pooled into a single device and thus enabling seamless data migration and storage tiering across heterogeneous storages.

 In the past I have seen very interesting use cases integrating server virtualization and storage virtualization. Listed below are some of the use cases

1) Seamless migration and tiering: 

     

    With the help of logical abstraction provided by the Storage virtualization appliance, host would be masked with a virtual volume and is completely unware of the underlying backend storage. Now with the help of native migration tool from the storage virtualization vendors underlying backend volumes that the virtual volume is made up of can be changed so that the host still has the access to virtual volume when the migration is being done. This helps in storage level tiering and migration across or within storage subsystem without a down time.

2) Vmotion across Datacenters:

What is vmotion ? its the capability to move a running VM from one ESX host to another, this is normaly done to offload the ESX server or to shutdown the host for maintenance. One of the requirement for this is a shared storage between the ESX hosts.
Now with the help of distributed device from storage virtualization solution from EMC which has legs spread across disparate datacenters, Vmotion can be done across Data centers (<100km | <5ms latency).  


What is distributed device ? Distributed devices are mirrored devices that spread across two VPLEX clusters connected together into a metro plex. Distributed devices are created on top of two devices, the devices should be from different VPLEX clusters. The geometry of distributed devices by default is Raid-1.

Encapsulating to virtualized storage platform with no downtime

Storage virtualization is now new wave in IT industry, most of the customers are now migrating to virtualized platform so that  they can prepare themself for another big thing, Cloud !

Now when it comes to moving the data from physical storage to virtualized platform, the pain point is how to do a migration with less downtime or no downtime

1) Migration with less downtime: Do the cabling and zoning prior to taking the downtime reflecting the new target pwwn's. Now when the maintenance window is scheduled, shutdown the application using the volume being migrated ( this would clear the SCSI reservation if any). Present the LUN to the virtualization appliance and create the virtual volume out of it and present this to host. For Virtual volume creation - refer the array config guide as applicable.
Now login to host and scan for the new volumes, the path for the volumes may change depending on the OS. Make necessary changes from host perspective so that the application can use the newly presented virtualized LUNs.

  2) Migration with no downtime: Migration can be done with no downtime using Vmware Storage vmotion. Present the new virtualised LUN to ESX host and then migrate the physical datastore to virtualised datastore using Storage VMotion.