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Re: VMs on external storage CPU overloading



On 7/30/2020 4:41 PM, Dan Ritter wrote:
john doe wrote:
Hi Debians,

I have limited space on my box, so I would like to install VMs onto an
external storage (usbkey 3.0) using Libvirt.

In the below command '/mnt/usbkey01' is the mountpoint for my usbkey:

virt-install --name=try01 --ram=1024
--disk=path=/mnt/usbkey01/machines/try01,size=6


My CPU overloads like crazy.

The overloading is related by the use of this usbkey but I don't
understand why?:
- Is this a Debian issue
- Is this a Libvirt issue
- Is this expected because I'm using virtualisation with KVM enabled


Other then increasing the size of my internal storage, can I do
something about it?


If I change the path to '/var/lib/machines/try01' (internal storage) it
works flowlessly and my CPU does not overload.

Two things:

- your CPU load, depending on how you measure it, may include
   processes which are waiting for I/O. This I/O is very slow,
   so.

- not all USB3 devices are the same. Many implement a
   single-request system, where the kernel is only allowed to
   make a read or write call, then wait for the response, then
   issue the next call. Anything describing itself as a "key"
   is particularly likely to have this.


Is there any way to verify this (command wize)?

Can you change your external storage?


Any suggestion?


Thanks DSR.

--
John Doe


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