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‘Boosting system utilization levels for storage’ is provided today by thin provisioning techniques. This delays actual storage capacity commitment to applications until actual write activity requires it. Combined with storage over-booking, the CFO today is attracted by saving potentials. Actual utilization levels for virtualized deployments may reach in the 80 percentile, whereas Gartner Group recently reported 42 percent for the industry average. Thin provisioning is available both in horizontal and vertical models and, in theory, similar capacity utilization ratios are technically achievable. Nevertheless, behaviors are different when considering a long period where disk array oversubscription carries the risk of capacity saturation and various mitigation scenarios possible with vertical virtualization fail short of matching the efficiency level achievable due to the elasticity provided by horizontal virtualization.
‘Increasing purchasing power for storage capacity’ is clearly better achieved with horizontal virtualization as replacement controllers can be acquired without the need to remain compatible with existing arrays. However, this needs to be put into perspective with the additional complexity brought by multiple storage technology vendors, the task to own the integration role and the ability to undertake a storage infrastructure virtualization project. These roles typically fall on the shoulders of IT operations and IT engineering, which may explain some initial reluctance to implementing an horizontal virtualization environment.
Looking at the industry momentum today, all major players are developing vertical virtualization solutions, which requires storage professionals to completely understand the pros and cons of these architecture variations especially as it relates to the cloud.
Clouds come with a new behavior promise for applications and drive an increasing demand on smart and versatile storage solutions with new needs, such as:
•Life cycle management of all components will be crucial – suspending storage services for traditional applications
because of upgrades or de-commissioning, will not be acceptable for cloud solutions.
•Data protection continuity will become more important, especially during component maintenance operations when
‘things may happen’.
•Geographically distributed storage solutions with continuous high availability will become required with desired features such
reduced effort for application protection set up and automation of site switch technique..
•Management of large data pools used by cloud applications will need to be delegated to the application virtualization layer
for rapid provisioning while cost and performance control and optimization will be required at storage layer with even less input from application owners.
•SLA enforcement and control, resource charge back and reinforced security models such as multi-tenancy will become
crucial for public Clouds.
Solutions for these requirements may result in architectures looking similar to the illustration below.
In the storage industry virtualization movement, standards have proven to be crucial and SNIA, like other standard bodies, are playing their specific role. This leaves a large share of autonomy to actual infrastructure designers. The author hopes that the content of this short article will provide good “food for thought” for the storage architects and managers when considering re-designing their solutions today for tomorrow and how it will all play in the cloud.
October/November 2011 I
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