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HTWingNut

Very Large Files (Virtual Machine Images) and Duplication

Question

Has anyone used duplication with very large files in DrivePool and with duplication enabled? How does DP manage large files? The VDI image would change relatively frequently since it's basically operating like an OS hard disk. Would the full file need to be duplicated every time or does it transfer just blocks of data? I'm talking about a virtual drive image that can be 3-4TB in size (or maybe more eventually).

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Didn't have a good experience with VHD files. I was using them to mount VirtualBox virtual machines. Eventually the VHDs became RAW, and I could no longer use them. There was data loss. Also I did have a few improper shutdowns (which could have been a contributor to the problem of VHDs getting corrupted.)

I have now saved the VHDs directly on the disk and not on the pool.

Another thing to note, duplication uses, me thinks, a simple file copy mechanism. So if you have those VHDs mounted and then you try to copy them without Volume Shadow Service, it doesn't turn out as expected. Once even one of the VMs crashed and started throwing errors. However if those VHDs are not mounted, it is a different scenario and they are just like any other large files.

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Thanks for the feedback. By "just like any other large file" does it copy it on the block level changes or full file change? Because if that file is changing regularly, doesn't seem very efficient to copy a full 3TB every time it changes. Which of course would be torture.

Either way, my VHD is on its own 8TB drive right now and I have a spare 8TB and think I will just mirror it. Probably safest solution.

Thanks!

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On 5/5/2020 at 8:42 AM, HTWingNut said:

does it copy it on the block level changes or full file change

It copies it like a file, full file change, not an image backup.

My understanding and observation is that if a VM is running and making changes to the virtual disk (duplication will cause errors). It happened with me, the virtualbox OS (ubuntu) started throwing errors and I'm guessing it was because of real time duplication of the VHD file.

Mirror would be the safest bet.

PS: I'm still recovering data from the ARQ backup. :blink:

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19 hours ago, drivepool_user said:

Mirror would be the safest bet.

Mirror using virtual hard disk NOT in-build disk management option. Otherwise you would be stuck with dynamic volumes which are not recognized by Drivepool and there is no way to convert them back to basic without reformatting them.

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Thanks. I ended up just setting up two 8TB HDD's mirrored outside of DrivePool through Disk Management. I don't see a need to add it to the DrivePool.

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