Saturday, October 18, 2008

greenBytes – an innovative approach energy efficient storage, but is it MAID?

MAID is a technology that has proven to be the most energy efficient online data storage currently available boasting potential of energy savings of up to 85% when compared to traditional array architectures. But the challenge has been to make this technology viable for smaller datastores where data volume is not measured in the multiple 100’s of terabytes if not petabytes. Small and medium size enterprises have the same needs and challenges as their larger brethren in managing unstructured, persistent, fixed content, archive class of data that tends to comprise 70% to 80% of enterprise data.

At SNW this week a new player, greenBytes ( )
introduced a technology designed to do just that. However, while there is no doubt that the Cypress® Storage Appliance is a very innovative solution is it really MAID or does it fall into the increasingly congested grouping of MAID like solutions, and if it does why should that matter?

First let us look at the Cypress Storage Appliance. It is based on the SUN 4540 platform and on the ZFS+ file system which has been relabeled greenBytes’ZFS+®. Among the features is real time, in-line data de-duplication, block level compression, remote replication, CIFS, NFS and iSCSI for both file and block applications and intelligent power management. Some innovative enhancements have been baked into ZFS by greenBytes enabling the MAID like functionality.

The evangelists at greenbytes are promoting a virtual storage pool capacity of over 90TB from a physical pool of 48x1TB drives, obviously with thanks to compression and data de-duplication, they claim a maximum power consumption of 1.2KW which is more like the system power draw of the 4540 and not maximum power input of 1.8KW, which is what should be measured. While they claim that they can deliver up to 80% saving in power consumption their industry leadership claimed of 26Watts/TB unfortunately falls short when compared to COPAN’s 10Watts/TB. However, the most interesting claim is an effective cost of less than $1/effective GB, if true that is getting down into tape territory making this an attractive option for VTL, D2D or indeed many other applications that want to offload persistent data from expensive online storage but still have online accessibility. I plan to write a bit more deeply on this technology so if interested send me an email and I will get you my findings when completed.

Back to the original question, is this MAID? If you stick to the original SNIA definition which calls for a maximum limit of 50% of the drives to be able to spin at any one time, the answer is no. Why is that important? Well it is all about power allocation and is why removable media has enjoyed such a power efficiency advantage over traditional online storage. When planning the power requirements for a data center the planners have to plan for the maximum possible power demand. Meaning, if all drives can spin at any one time then that is the load that should be used. Removable media stacked on racks do not have any power demands, only space. This is analogous to MAID.

A Maid system architecturally limits the number of disks that can spin at any one time. So just like a tape or optical library data can be stored on a medium that is not consuming energy. Because there is an energy budget which cannot be exceeded, drives in a MAID system may have to spin down before requested drives can spin up. This means that not only is energy waste on non-productive spinning drives eliminated but power does not have to be allocated to support all disks in the array, only for that percentage that can spin simultaneously. This unique attribute of MAID can be particularly beneficial in those situations where additional power is simply not available or securing its availability exorbitantly expensive.

Classic MAID or not the Cypress® Storage Appliance is a very interesting approach to delivering an energy efficient, online storage solution and may prove to have more mainstream applicability than traditional MAID, certainly it is worth a close look. I look forward to watching the companies progress as it roles out this innovative solution.

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