Cirrus Data: Migration for blockheads

Block data migration provides an exact copy of data from a source storage system to a target system.  Blocks and Files has written about file and object-level migrations with Datadobi, Komprise, and WANdisco, but little about block-level migrations. Enter Cirrus Data Solutions, which offers Cirrus Migrate On-Premises to move data at block level between Storage Area Network (SAN) arrays.

There’s no need to reboot, change multi-path drivers or modify existing SAN zoning when migrating data. A second Cirrus Migrate Cloud product moves block data from an on-premises system to the public clouds including AWS, Azure, GCP and Oracle, and is present in the marketplaces for each of these clouds.

Block-level data migrations can involve complexities such as installing drivers at the hosts, changing FC zones, and LUN masking, with SAN downtime required to sort them out. Cirrus has its own patented Transparent Datapath Intercept (TDI) software technology to fix these problems. 

Cirrus Data graphic
Cirrus Data graphic

This is embodied in a physical appliance, the DMS (Data Migration Server) appliance, that is hooked up in the data path; to the Fibre Channel or iSCSI Ethernet cable between the SAN target and the Fibre Channel/Ethernet switch. For example, Cirrus Data says: “The appliance should look like a wire when installed to both the hosts and storage. The installation process is a matter of removing each FC connection between the switch and storage and connecting it on the appliance; a process that takes just 5 seconds per path! To install an appliance with 4 paths, the total time is less than a minute, and in an HA solution, less that 2 minutes. And if there is ever a problem, the appliances can be uninstalled just as fast.” 

Cirrus Data appliances
Cirrus Data appliances

Cirrus says there are there steps in the migration process: inserting the appliance, migrating the data, and cutover. It has four named elements as part of its software offering:

  • TDI – transparently intercepts SAN traffic without downtime and enables a copy to be made and transmitted to the new array or cloud. It eliminates, Cirrus Data says, all the pain points associated with inserting an in-band appliance to a live FC or iSCSI SAN. It can be inserted logically or physically.
  • iQoS (Intelligent Quality of Service) – monitors individual I/Os to ensure there is no migrate application impact to the host and to dynamically utilize breaks in production traffic to migrate more data through to the new array. 
  • pMotion – emulates the old array to the hosts, which are actually running on the new storage array. While this is being used the old array can be removed.
  • cMotion – carries out  storage-level cut-over from a source to the target system without downtime to the source host, once the old array is removed, if not before. It swings the workload over from the original FC or iSCSI source system to the destination array.

A video provides more information:

Cirrus Data’s technology can also be used in Cirrus Protect On-Premises to continuously protect a SAN array by building and maintaining a copy in a remote data center.


Pure Storage offers a block data migration service moving data from other suppliers’ SAN systems to its own FlashArray storage. 

DataCore offers a similar service with its SANsymphony software. RiverMeadow also offers block data migration services to the cloud, providing live migration of database and message queue-related application workloads. Its service uses an application-consistent snapshot to enable live migration without open file concerns.


Cirrus Data Solutions was started in New York in 2011 by brothers Wayne Lam, Chairman and CEO and Wai Lam, who is CTO and VP of Engineering, funded by a $480,000 seed round and then $3.2 million in debt financing. A $2.5 million venture round took place in January this year. That funding is paying for new sales and marketing activities.

The company developed and patented its Transparent Datapath Intercept (TDI) technology to enable customers to bring new storage architectures online without downtime. This formed the basis of product offerings which culminated in the Cirrus Migrate Cloud introduced in 2021. Cirrus holds 30 patents, 11 concerning TDI.

Wayne and Wai Lam were co-founders at FalconStor Software in 2000. Wai Lam served as CTO and VP of Engineering, being Falconstor’s chief architect, and responsible for 23 of 34 FalconStor patents.

Wayne Lam was, Cirrus Data says, largely responsible for most of FalconStor’s successful storage products (think IPStor). He was a senior executive at CA Technologies before that, and Cheyenne Software, prior to its acquisition by CA.