[Sheepdog] Q: stripping / robustness / kvm resume+suspend / ..

MORITA Kazutaka morita.kazutaka at lab.ntt.co.jp
Sat Dec 5 15:07:46 CET 2009


On 12/05/2009 04:48 AM, Daniel Schwager wrote:
> Hi MORITA Kazutaka,
> first of all - I would like to thank you for this great
> project - I like your approach (independent of the java dependency ;-)

I'm glad that many people are interested in this project!

> Before (practicaly) starting evaluation, I would like to know some
> simple issues:
> 1. is it possible to use sheepdog as storage for resuming/suspending
>    KVM machines ? Normaly, kvm invokes a command like dd or cat to
>    store/restore the RAM to/from disk ... this may will not work
>    with sheepdog in the current version, or ? 

Not supported yet, but it will be supported in future.
To support resuming/suspending, sheepdog need to support online
snapshot. It is included in our TODO list.

> 2. to be sure - the KVM machines could run on a sheepdog  server member,
>    but can also run on not-sheepdog-server machine connecting
>    to the sheepdog cluster via IP and multicast.

It may be possible to support vm runs outside sheepdog servers.
We currently assume virtual machines run on sheepdog server machines
to enable zero-hop data accessing and to check vm is alive.
We can think of removing this restriction if it is needed.

> 3. Can i change the "stipping" (means count of servers "hosting" the
> same data blocks)
>    after I created the cluster ? Sure - I can add some servers to
> increase
>    HDD-storage - but can I change the stripping from e.g. 3 to 5 to
> increase
>    performance ?

Yes, you can. However current implementation don't move existing data
when the number of servers is changed, and dynamic server membership
change is not well tested. This is the most important TODO item.

> 4. KVM-server - can I configure the kvm-server (hosting the kvm-vm's) 
>    to using ethernet trunking (2 x 1GBit) - or does this cause problems
>    with the multicast sheepdog communication to the kvm-server ?

I don't have an environment to test it, but it is problably no problem.

> 5. Robustness 
>    - could it be used for productive enviroment (what's your feeling ;-)
>    - do you have some running productive enviroment based on sheepdog
>      (beside of your test bed)

We are working with sheepdog so that it can be. :)
But, to be honest, it currently lacks some critical features such as
data deletion support, automatic data recovery, etc, so we don't use
sheepdog for productive environment yet.
We'll implement these features in several months.
If sheepdog could be used for productive purpose, it would be after


MORITA Kazutaka

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