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Problems with dynamic disk information under Windows

We've got an STK D280 with a StoreAge SVM controlling it all. One problem that has come to light is dynamic disks vs. basic disks. The problem is that dynamic disks are expandable so that if we need to we can increase volume sizes automatically if necessary. The down side to this is that we can't mount more than one view of these volumes on any server, let alone the one it was created from. Basic disks on the other hand allow us to mount as many views as we like even on the same server. They are, however, unexpandable so we're kind of stuck.

Is this something peculiar to StorAge or do all the vendors have this issue? I'd like to be able to mount an expandable volume on a server and take snapshots of the data rather than the volume. It would be nice to be able to increase the volume size but make the views/snaps independent of the original volume or at least have a choice. I'd like to mount these snaps on the same server and provide users the capability of getting their data back from say hourly snapshots themselves. Any ideas?

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Yeah, everyone has the same problem in a Windows environment since the dynamic disk information under Windows is stored in the registry and not the drive itself. Dynamic disks and volume sets are not supported very well under a Microsoft cluster server for that very reason. Registry data is local to the system.

Since disk manager in Windows 2000 is a subset of the complete Veritas solution, then purchasing the complete Veritas file system suite may solve your problem. You may be able to get around this by exporting the HKLMCurrentControlSetServicesDisk parameters and then importing them on a machine that has the exact same configuration. Or, use the FTEDIT utility from the resource kit to recreate the proper disk sequence on the server that imports the other systems disk registry settings.

Another approach is to use a storage solution or virtualization software that provides expandable LUNS under Windows basic disks. When I was at Compaq, they had a solution called "Virtual Replicator", that allowed dynamic expansion of basic disks under Windows NT. Perhaps it is still available but the solution was Windows only and was a software solution. Access to the virtual volumes was over IP and multiple metadata snapshots could be created.


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This was first published in September 2003

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