[Sheepdog] [PATCH] sheep: disable object cache by default

[Liu Yuan]

On 05/10/2012 10:37 PM, Christoph Hellwig wrote:

>> What did you mean by en/disable it on a per VDI basis? I think object
>> > cache does have this attribute, in terms of QEMU command line option. Or
>> > I miss some context?
> Have an attribute on the sheepdog_inode that the object cache is used
> for access to this VDI, without having to coordinate all possible users
> of it, e.g. a way to specify it when creating the vdi and having any
> user simpliy do the right thing.


>> What did you mean by en/disable it on a per VDI basis? I think object
>> > cache does have this attribute, in terms of QEMU command line
option. Or
>> > I miss some context?
> Have an attribute on the sheepdog_inode that the object cache is used
> for access to this VDI, without having to coordinate all possible users
> of it, e.g. a way to specify it when creating the vdi and having any
> user simpliy do the right thing.

I don't think it make any sense. This just complicate the things, for
now we have a global switch and per VDI switch already, any attempt to
introduce yet another switch looks really crazy to me. Maybe it would
help your use case, but I think you should be aware:

1) Sheepdog originally targets for mixing computing and storage in one
cluster to maximize the resource usage.
2) Sheepdog isn't inherently optimized for users who has extremely
high-end and fast network.

I think we are coding sheepdog for general setup, where we have low-end
servers with ordinary network connect and try to cluster them together
to get a better utilized and elastic computing and storage.

I think with current global and per VDI switch for object cache, nothing
technically stops you from achieving your personal target at your own will.

Thanks,
Yuan