The highlight of the HP August storage announcement is HP Peer Motion. In a nutshell, it is VMware’s Storage vMotion without the "v" overhead. This allows active volumes to be dynamically and permanently moved between either two HP 3PAR arrays or two HP LeftHand arrays. The homogeneous arrays must be situated within metro distances.
The key benefit for this feature is the reduction in cost and complexity of array migrations. In a detailed Wikibon study, the time to provision new arrays averaged 5 months, and array migration costs exceeded $50,000 per migration. For a typical array this represents additional costs above the original hardware and software expenditures of:
- Loss on buying earlier than required....... ~13%
- Loss on lease payments......................... ~13%
- Cost of array migration......................... ~17%
- Total cost............................................. ~43% of acquisition cost.
Migrations require shutting down the application for a period of time, which is disruptive to business users and an additional business cost.
The other area of advantage is in providing the equivalent of a VMware Storage vMotion for high performance applications. By offloading the entire process to the arrays, the data from more mission critical applications will be able to be moved in both bare-metal and virtualized environments. Storage vMotion has some good features; for example, in vSphere 5.0 there is a is called Mirror Mode and it enables make duplicate writes to both the current and the moved volumes. But the bottom line is that the performance and management overhead of running the process through the server is high, with significant complexity and failure rate. This makes it unsuitable for high performance high value applications. The Peer Motion is completely transparent to the host - the only changes that need to be made are to lin management of the multi-pathing software.
Although in theory this feature could be used to dynamically or frequently balance storage workloads between arrays, there are overheads on the storage network and operational risks that in most cases should be avoided if at all possible. All migrations and transfers should be planned well ahead of time and executed out of prime time. Having powerful features like Peer Motion increases the need for strong change control for production environments.
The only other federated solutions alternative to HP Peer Motion are the more limited Federated Live Migration on EMC VMAX arrays on Tier 1 arrays (available in June 2011), and Dell Compellent's excellent Live Volume (quietly improved since its initial announcement in 2008). The virtualization solutions such as EMC's VPLEX, Hitachi's USP & VSP, and IBM's SVC allow migration between heterogeneous virtualized arrays, but once virtualized they cannot migrate non-disruptively to native mode, and can't be moved from one virtualization appliance to another.
Availability of HP Peer Motion is immediate (8/29/2011). Arrays under existing support contracts for HP LeftHand Storage Systems can be upgraded to the latest operating environments, which will include Peer Motion, at no additional charge. The software for HP 3PAR arrays is licensed by drive type for a specific array model with several pricing options and SKU’s. The cost range for a single Peer Motion license on each target array is between a minimum of $6,000 on the entry models to a maximum of about $25,000 on the highest level models (some 3PAR arrays may require multiple licenses).
The HP Peer Motion is an excellent feature on both the HP 3PAR and HP LeftHand arrays and can be justified by just the initial migration. Wikibon unreservedly recommends careful adoption in the data center for migration and well managed transfer of data.
Action Item: Installations using HP 3PAR and LeftHand arrays should use this feature on all new array migrations and should include its benefits in any business case for new storage.