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Should making a new Wubi disk take a very long time?

I am currently following along to the steps in this answer for increasing the root partition space for my Ubuntu Wubi install: Increase size of root partition after installing Ubuntu in Windows

The current size of my root is 30 GB. I am trying to make a new disk with 400 GB, so I ran the following command:

/host/ubuntu/disks# dd if=/dev/zero of=new.disk bs=1MB count=400000

It's been running for the last 20 minutes, so I'm a little worried something may have gone afoul, but it could be working fine. Should creating this partition take a long time since it's large? This isn't even the formatting step, so I figured it would be fast, but I could definitely be wrong.

EDIT: The disk I am doing this on is two 1 TB drives in a raid 1, with the following space:

root@ubuntu:/home/jsage8# df -h /host
Filesystem      Size  Used Avail Use% Mounted on
/dev/sdc1       932G  259G  674G  28% /host

EDIT: This has now been running for over an hour. I'm hesitant to kill it in the middle though as I'm not sure what type of ramifications that might have?

share|improve this question
400 GB? That is not a good idea. Please cancel and do a normal install. It will take forever and probably break (if it even works). It's safe to Ctrl+C and wait for it to cancel, and then delete the /host/ubuntu/disks/new.disk. – bcbc Oct 25 '13 at 17:37
Yeah I think I probably should do that. It did end up finishing successfully in the end, but I might just delete it and make a partition and install it there. If anyone else is having a similar concern this took 1.7 hours to complete and that's without even formatting it. – sage88 Oct 25 '13 at 18:52
You're creating a 400 GB file out of 1 MB blocks. This takes time. You could instead create a sparse file (using the seek= option), but in general using a 400 GB virtual disk is too risky (all data can be lost if the underlying root.disk file is corrupted). – bcbc Oct 25 '13 at 19:50

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