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I'm running CentOS with Xen hypervisor. I've two virtual machines running on it (2 DomU and obviously 1 Dom0). I've two hard disks that I'm trying to dedicate exclusively to each of the DomU. This is basically to experiment with the performance of the VM's. If the two VM share the same disk then the disk read and write might be terribly slow compared to using dedicated drives. I'm trying to analyse advantages like that by the usage of separate hard disks.

How can I do this i.e. How can I assign separate Hard Disks to the VMs? Does Dom0 require a hard disk too?

Any help is appreciated.

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Yes, you must have some sort of storage device to run dom0. It doesn't have to be a traditional HDD - it could be a flash card, USB stick, SSD, or network boot (iSCSI, FC, etc.). You can even use some Live CD/DVD distributions. Once you have dom0 up and running you can assign you HDDs to the guest. Let's say dom0 uses disk sda and you also have disks sdb and sdc. You can assign the following to your two guests: phy:/dev/sdb Phy:/dev/sdc

This will dedicate those entire HDDs to the guests. However, unless you're doing some very disk-intensive loads (database, e-mail system), I doubt you'll hit a situation where you will see noticeable impact if you share HDDs between multiple guests.

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